\input{titlepag.tex}
\part{Gnuplot}
\section{Copyright}
\preverbatim
\begin{verbatim}
     Copyright (C) 1986 - 1993, 1998   Thomas Williams, Colin Kelley
\end{verbatim}
\postverbatim

Permission to use, copy, and distribute this software and its
documentation for any purpose with or without fee is hereby granted,
provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation.

Permission to modify the software is granted, but not the right to
distribute the complete modified source code.  Modifications are to
be distributed as patches to the released version.  Permission to
distribute binaries produced by compiling modified sources is granted,
provided you
\preverbatim
\begin{verbatim}
 1. distribute the corresponding source modifications from the
  released version in the form of a patch file along with the binaries,
 2. add special version identification to distinguish your version
  in addition to the base release version number,
 3. provide your name and address as the primary contact for the
  support of your modified version, and
 4. retain our contact information in regard to use of the base
  software.
\end{verbatim}
\postverbatim
Permission to distribute the released version of the source code along
with corresponding source modifications in the form of a patch file is
granted with same provisions 2 through 4 for binary distributions.

This software is provided {\tt"}as is{\tt"} without express or implied warranty
to the extent permitted by applicable law.


\preverbatim
\begin{verbatim}
     AUTHORS
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     Original Software:
        Thomas Williams,  Colin Kelley.
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     Gnuplot 2.0 additions:
        Russell Lang, Dave Kotz, John Campbell.
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     Gnuplot 3.0 additions:
        Gershon Elber and many others.
\end{verbatim}
\postverbatim
\section{Introduction}
{\bf gnuplot} is a command-driven interactive function and data plotting program.
It is case sensitive (commands and function names written in lowercase are
not the same as those written in CAPS).  All command names may be abbreviated
as long as the abbreviation is not ambiguous.  Any number of commands may
appear on a line (with the exception that {\bf load} or {\bf call} must be the final
command), separated by semicolons (;).  Strings are indicated with quotes.
They may be either single or double quotation marks, e.g.,

\preverbatim
\begin{verbatim}
     load "filename"
     cd 'dir'
\end{verbatim}
\postverbatim

although there are some subtle differences (see {\bf syntax} for more details).

Any command-line arguments are assumed to be names of files containing
{\bf gnuplot} commands, with the exception of standard X11 arguments, which are
processed first.  Each file is loaded with the {\bf load} command, in the order
specified.  {\bf gnuplot} exits after the last file is processed.  When no load
files are named, {\bf gnuplot} enters into an interactive mode.  The special
filename {\tt"}-{\tt"} is used to denote standard input.  See {\tt"}help batch/interactive{\tt"}
for more details.

Many {\bf gnuplot} commands have multiple options.  These options must appear in
the proper order, although unwanted ones may be omitted in most cases.  Thus
if the entire command is {\tt"}command a b c{\tt"}, then {\tt"}command a c{\tt"} will probably
work, but {\tt"}command c a{\tt"} will fail.

Commands may extend over several input lines by ending each line but the last
with a backslash ($\backslash$).  The backslash must be the {\em last\/} character on each
line.  The effect is as if the backslash and newline were not there.  That
is, no white space is implied, nor is a comment terminated.  Therefore,
commenting out a continued line comments out the entire command (see
{\bf comment}).  But note that if an error occurs somewhere on a multi-line
command, the parser may not be able to locate precisely where the error is
and in that case will not necessarily point to the correct line.

In this document, curly braces (\{\}) denote optional arguments and a vertical
bar ($|$) separates mutually exclusive choices.  {\bf gnuplot} keywords or {\bf help}
topics are indicated by backquotes or {\bf boldface} (where available).  Angle
brackets ($<$$>$) are used to mark replaceable tokens.  In many cases, a default
value of the token will be taken for optional arguments if the token is
omitted, but these cases are not always denoted with braces around the angle
brackets.

For on-line help on any topic, type {\bf help} followed by the name of the topic
or just {\bf help} or {\bf ?} to get a menu of available topics.

The new {\bf gnuplot} user should begin by reading about {\bf plotting} (if on-line,
type {\bf help plotting}).
\section{Seeking-assistance}
There is a mailing list for {\bf gnuplot} users.  Note, however, that the
newsgroup
\preverbatim
\begin{verbatim}
     comp.graphics.apps.gnuplot
\end{verbatim}
\postverbatim
is identical to the mailing list (they both carry the same set of messages).
We prefer that you read the messages through the newsgroup rather than
subscribing to the mailing list.  Administrative requests should be sent to
\preverbatim
\begin{verbatim}
     majordomo@dartmouth.edu
\end{verbatim}
\postverbatim
Send a message with the body (not the subject) consisting of the single word
{\tt"}help{\tt"} (without the quotes) for more details.

The address for mailing to list members is:
\preverbatim
\begin{verbatim}
     info-gnuplot@dartmouth.edu
\end{verbatim}
\postverbatim

Bug reports and code contributions should be mailed to:
\preverbatim
\begin{verbatim}
     bug-gnuplot@dartmouth.edu
\end{verbatim}
\postverbatim

The list of those interested in beta-test versions is:
\preverbatim
\begin{verbatim}
     info-gnuplot-beta@dartmouth.edu
\end{verbatim}
\postverbatim

There is also a World Wide Web page with up-to-date information, including
known bugs:
\preverbatim
\begin{verbatim}
     http://www.cs.dartmouth.edu/gnuplot_info.html
\end{verbatim}
\postverbatim

Before seeking help, please check the
FAQ (Frequently Asked Questions) list.
If you do not have a copy of the FAQ, you may request a copy by email from
the Majordomo address above, ftp a copy from
\preverbatim
\begin{verbatim}
     ftp://ftp.ucc.ie/pub/gnuplot/faq,
     ftp://ftp.gnuplot.vt.edu/pub/gnuplot/faq,
\end{verbatim}
\postverbatim
or see the WWW {\bf gnuplot} page.

When posting a question, please include full details of the version of
{\bf gnuplot}, the machine, and operating system you are using.  A {\em small\/} script
demonstrating the problem may be useful.  Function plots are preferable to
datafile plots.  If email-ing to info-gnuplot, please state whether or not
you are subscribed to the list, so that users who use news will know to email
a reply to you.  There is a form for such postings on the WWW site.
\section{What's New in version 3.7}
Gnuplot version 3.7 contains many new features.  This section gives a partial
list and links to the new items in no particular order.

1. {\bf fit f(x) 'file' via} uses the Marquardt-Levenberg method to fit data.
(This is only slightly different from the {\bf gnufit} patch available for 3.5.)

2. Greatly expanded {\bf using} command.  See {\bf plot using}.

3. {\bf set timefmt} allows for the use of dates as input and output for time
series plots.  See {\bf Time/Date data} and
timedat.dem.

4. Multiline labels and font selection in some drivers.

5. Minor (unlabeled) tics.  See {\bf set mxtics}.

6. {\bf key} options for moving the key box in the page (and even outside of the
plot), putting a title on it and a box around it, and more.  See {\bf set key}.

7. Multiplots on a single logical page with {\bf set multiplot}.

8. Enhanced {\bf postscript} driver with super/subscripts and font changes.
(This was a separate driver ({\bf enhpost}) that was available as a patch for
3.5.)

9. Second axes:  use the top and right axes independently of the bottom and
left, both for plotting and labels.  See {\bf plot}.

10. Special datafile names {\bf '-'} and {\bf {\tt"}{\tt"}}.  See {\bf plot special-filenames}.

11. Additional coordinate systems for labels and arrows.  See {\bf coordinates}.

12. {\bf set size} can try to plot with a specified aspect ratio.

13. {\bf set missing} now treats missing data correctly.

14. The {\bf call} command: {\bf load} with arguments.

15. More flexible {\bf range} commands with {\bf reverse} and {\bf writeback} keywords.

16. {\bf set encoding} for multi-lingual encoding.

17. New {\bf x11} driver with persistent and multiple windows.

18. New plotting styles: {\bf xerrorbars}, {\bf histeps}, {\bf financebars} and more.
See {\bf set style}.

19. New tic label formats, including {\bf {\tt"}\%l \%L{\tt"}} which uses the mantissa and
exponents to a given base for labels.  See {\bf set format}.

20. New drivers, including {\bf cgm} for inclusion into MS-Office applications
and {\bf gif} for serving plots to the WEB.

21. Smoothing and spline-fitting options for {\bf plot}.  See {\bf plot smooth}.

22. {\bf set margin} and {\bf set origin} give much better control over where a
graph appears on the page.

23. {\bf set border} now controls each border individually.

24. The new commands {\bf if} and {\bf reread} allow command loops.

25. Point styles and sizes, line types and widths can be specified on the
{\bf plot} command.  Line types and widths can also be specified for grids,
borders, tics and arrows.  See {\bf plot with}.  Furthermore these types may be
combined and stored for further use.  See {\bf set linestyle}.

26. Text (labels, tic labels, and the time stamp) can be written vertically
by those terminals capable of doing so.
\section{Batch/Interactive Operation}
{\bf gnuplot} may be executed in either batch or interactive modes, and the two
may even be mixed together on many systems.

Any command-line arguments are assumed to be names of files containing
{\bf gnuplot} commands (with the exception of standard X11 arguments, which are
processed first).  Each file is loaded with the {\bf load} command, in the order
specified.  {\bf gnuplot} exits after the last file is processed.  When no load
files are named, {\bf gnuplot} enters into an interactive mode.  The special
filename {\tt"}-{\tt"} is used to denote standard input.

Both the {\bf exit} and {\bf quit} commands terminate the current command file and
{\bf load} the next one, until all have been processed.

Examples:

To launch an interactive session:
\preverbatim
\begin{verbatim}
     gnuplot
\end{verbatim}
\postverbatim

To launch a batch session using two command files {\tt"}input1{\tt"} and {\tt"}input2{\tt"}:
\preverbatim
\begin{verbatim}
     gnuplot input1 input2
\end{verbatim}
\postverbatim

To launch an interactive session after an initialization file {\tt"}header{\tt"} and
followed by another command file {\tt"}trailer{\tt"}:
\preverbatim
\begin{verbatim}
     gnuplot header - trailer
\end{verbatim}
\postverbatim
\section{Command-line-editing}
Command-line editing is supported by the Unix, Atari, VMS, MS-DOS and OS/2
versions of {\bf gnuplot}.  Also, a history mechanism allows previous commands to
be edited and re-executed.  After the command line has been edited, a newline
or carriage return will enter the entire line without regard to where the
cursor is positioned.

(The readline function in {\bf gnuplot} is not the same as the readline used in
GNU Bash and GNU Emacs.  If the GNU version is desired, it may be selected
instead of the {\bf gnuplot} version at compile time.)


The editing commands are as follows:


\begin{center}
\begin{tabular}{|cl|} \hline
\multicolumn{2}{|c|}{Command-line Editing Commands} \\ \hline \hline
Character & Function \\ \hline
 & \multicolumn{1}{|c|}{Line Editing}\\ \cline{2-2}
\verb~^B~ & move back a single character.\\
\verb~^F~ & move forward a single character.\\
\verb~^A~ & move to the beginning of the line.\\
\verb~^E~ & move to the end of the line.\\
\verb~^H, DEL~ & delete the previous character.\\
\verb~^D~ & delete the current character.\\
\verb~^K~ & delete from current position to the end of line.\\
\verb~^L, ^R~ & redraw line in case it gets trashed.\\
\verb~^U~ & delete the entire line. \\
\verb~^W~ & delete from the current word to the end of line. \\ \hline
 & \multicolumn{1}{|c|}{History} \\ \cline{2-2}
\verb~^P~ & move back through history.\\
\verb~^N~ & move forward through history.\\
\hline
\end{tabular}
\end{center}

On the IBM PC, the use of a TSR program such as DOSEDIT or CED may be desired
for line editing.  The default makefile assumes that this is the case;  by
default {\bf gnuplot} will be compiled with no line-editing capability.  If you
want to use {\bf gnuplot}'s line editing, set READLINE in the makefile and add
readline.obj to the link file.  The following arrow keys may be used on the
IBM PC and Atari versions if readline is used:


\begin{center}
\begin{tabular}{|cl|} \hline
Arrow key  & Function \\ \hline
Left       & same as \verb~^B~. \\
Right      & same as \verb~^F~. \\
Ctrl Left  & same as \verb~^A~. \\
Ctrl Right & same as \verb~^E~. \\
Up         & same as \verb~^P~. \\
Down       & same as \verb~^N~. \\
\hline
\end{tabular}
\end{center}

The Atari version of readline defines some additional key aliases:


\begin{center}
\begin{tabular}{|cl|} \hline
Arrow key & Function \\ \hline
Undo      & same as \verb~^L~. \\
Home      & same as \verb~^A~. \\
Ctrl Home & same as \verb~^E~. \\
Esc       & same as \verb~^U~. \\
Help      & `{\bf help}' plus return. \\
Ctrl Help & `{\bf help }'. \\
\hline
\end{tabular}
\end{center}
\section{Comments}
Comments are supported as follows: a {\bf \#} may appear in most places in a line
and {\bf gnuplot} will ignore the rest of the line.  It will not have this effect
inside quotes, inside numbers (including complex numbers), inside command
substitutions, etc.  In short, it works anywhere it makes sense to work.
\section{Coordinates}
The commands {\bf set arrow}, {\bf set key}, and {\bf set label} allow you to draw
something at an arbitrary position on the graph.  This position is specified
by the syntax:

\preverbatim
\begin{verbatim}
     {<system>} <x>, {<system>} <y> {,{<system>} <z>}
\end{verbatim}
\postverbatim

Each $<$system$>$ can either be {\bf first}, {\bf second}, {\bf graph} or {\bf screen}.

{\bf first} places the x, y, or z coordinate in the system defined by the left
and bottom axes; {\bf second} places it in the system defined by the second axes
(top and right); {\bf graph} specifies the area within the axes --- 0,0 is bottom
left and 1,1 is top right (for splot, 0,0,0 is bottom left of plotting area;
use negative z to get to the base --- see {\bf set ticslevel}); and {\bf screen}
specifies the screen area (the entire area --- not just the portion selected by
{\bf set size}), with 0,0 at bottom left and 1,1 at top right.

If the coordinate system for x is not specified, {\bf first} is used.  If the
system for y is not specified, the one used for x is adopted.

If one (or more) axis is timeseries, the appropriate coordinate should
be given as a quoted time string according to the {\bf timefmt} format string.
See {\bf set xdata} and {\bf set timefmt}.  {\bf gnuplot} will also accept an integer
expression, which will be interpreted as seconds from 1 January 2000.
\section{Environment}
A number of shell environment variables are understood by {\bf gnuplot}.  None of
these are required, but may be useful.

If GNUTERM is defined, it is used as the name of the terminal type to be
used.  This overrides any terminal type sensed by {\bf gnuplot} on start-up, but
is itself overridden by the .gnuplot (or equivalent) start-up file (see
{\bf start-up}) and, of course, by later explicit changes.

On Unix, AmigaOS, AtariTOS, MS-DOS and OS/2, GNUHELP may be defined to be the
pathname of the HELP file (gnuplot.gih).

On VMS, the logical name GNUPLOT\$HELP should be defined as the name of the
help library for {\bf gnuplot}.  The {\bf gnuplot} help can be put inside any system
help library, allowing access to help from both within and outside {\bf gnuplot}
if desired.

On Unix, HOME is used as the name of a directory to search for a .gnuplot
file if none is found in the current directory.  On AmigaOS, AtariTOS,
MS-DOS and OS/2, gnuplot is used.  On VMS, SYS\$LOGIN: is used. See {\bf help
start-up}.

On Unix, PAGER is used as an output filter for help messages.

On Unix, AtariTOS and AmigaOS, SHELL is used for the {\bf shell} command.  On
MS-DOS and OS/2, COMSPEC is used for the {\bf shell} command.

On MS-DOS, if the BGI or Watcom interface is used, PCTRM is used to tell
the maximum resolution supported by your monitor by setting it to
S$<$max. horizontal resolution$>$. E.g. if your monitor's maximum resolution is
800x600, then use:
\preverbatim
\begin{verbatim}
     set PCTRM=S800
\end{verbatim}
\postverbatim
If PCTRM is not set, standard VGA is used.

FIT{\tt\_}SCRIPT may be used to specify a {\bf gnuplot} command to be executed when a
fit is interrupted --- see {\bf fit}.  FIT{\tt\_}LOG specifies the filename of the
logfile maintained by fit.
\section{Expressions}
In general, any mathematical expression accepted by C, FORTRAN, Pascal, or
BASIC is valid.  The precedence of these operators is determined by the
specifications of the C programming language.  White space (spaces and tabs)
is ignored inside expressions.

Complex constants are expressed as \{$<$real$>$,$<$imag$>$\}, where $<$real$>$ and $<$imag$>$
must be numerical constants.  For example, \{3,2\} represents 3 + 2i; \{0,1\}
represents 'i' itself.  The curly braces are explicitly required here.

Note that gnuplot uses both {\tt"}real{\tt"} and {\tt"}integer{\tt"} arithmetic, like FORTRAN and
C.  Integers are entered as {\tt"}1{\tt"}, {\tt"}-10{\tt"}, etc; reals as {\tt"}1.0{\tt"}, {\tt"}-10.0{\tt"}, {\tt"}1e1{\tt"},
3.5e-1, etc.  The most important difference between the two forms is in
division: division of integers truncates: 5/2 = 2; division of reals does
not: 5.0/2.0 = 2.5.  In mixed expressions, integers are {\tt"}promoted{\tt"} to reals
before evaluation: 5/2e0 = 2.5.  The result of division of a negative integer
by a positive one may vary among compilers.  Try a test like {\tt"}print -5/2{\tt"} to
determine if your system chooses -2 or -3 as the answer.

The integer expression {\tt"}1/0{\tt"} may be used to generate an {\tt"}undefined{\tt"} flag,
which causes a point to ignored; the {\bf ternary} operator gives an example.

The real and imaginary parts of complex expressions are always real, whatever
the form in which they are entered: in \{3,2\} the {\tt"}3{\tt"} and {\tt"}2{\tt"} are reals, not
integers.
\subsection{Functions}
The functions in {\bf gnuplot} are the same as the corresponding functions in
the Unix math library, except that all functions accept integer, real, and
complex arguments, unless otherwise noted.

For those functions that accept or return angles that may be given in either
degrees or radians (sin(x), cos(x), tan(x), asin(x), acos(x), atan(x),
atan2(x) and arg(z)), the unit may be selected by {\bf set angles}, which
defaults to radians.


\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{Math library functions} \\ \hline \hline
Function & Arguments & Returns \\ \hline
abs(x) & any  &  absolute value of $x$, $|x|$; same type \\
abs(x) & complex &  length of $x$, $\sqrt{{\mbox{real}(x)^{2} +
\mbox{imag}(x)^{2}}}$ \\
acos(x) & any  & $\cos^{-1} x$ (inverse cosine) \\
acosh(x) & any  & $\cosh^{-1} x$ (inverse hyperbolic cosine) in radians \\
arg(x) & complex & the phase of $x$ \\
asin(x) & any  & $\sin^{-1} x$ (inverse sin) \\
asinh(x) & any  & $\sinh^{-1} x$ (inverse hyperbolic sin) in radians \\
atan(x) & any  & $\tan^{-1} x$ (inverse tangent) \\
atan2(y,x) & int or real & $\tan^{-1} (y/x)$ (inverse tangent) \\
atanh(x) & any  & $\tanh^{-1} x$ (inverse hyperbolic tangent) in radians \\
besj0(x) & int or real &  $j_{0}$ Bessel function of $x$, in radians \\
besj1(x) & int or real & $j_{1}$ Bessel function of $x$, in radians \\
besy0(x) & int or real & $y_{0}$ Bessel function of $x$, in radians \\
besy1(x) & int or real & $y_{1}$ Bessel function of $x$, in radians \\
ceil(x) & any & $\lceil x \rceil$, smallest integer not less than $x$
(real part) \\
cos(x) & any & $\cos x$, cosine of $x$ \\
cosh(x) & any & $\cosh x$, hyperbolic cosine of $x$ in radians \\
erf(x) & any & $\mbox{erf}(\mbox{real}(x))$,  error function of real($x$) \\
erfc(x) & any & $\mbox{erfc}(\mbox{real}(x))$,  1.0 - error function of real($x$) \\
exp(x) & any & $e^{x}$,  exponential function of $x$ \\
floor(x) & any & $\lfloor x \rfloor$,  largest integer not greater
than $x$ (real part) \\
gamma(x) & any & $\mbox{gamma}(\mbox{real}(x))$,  gamma function of real($x$) \\
ibeta(p,q,x) & any & $\mbox{ibeta}(\mbox{real}(p,q,x))$,  ibeta function of real($p$,$q$,$x$) \\
inverf(x) & any &  inverse error function of real($x$)  \\
igamma(a,x) & any & $\mbox{igamma}(\mbox{real}(a,x))$,  igamma function of real($a$,$x$) \\
imag(x) & complex &  imaginary part of $x$ as a real number \\
invnorm(x) & any &  inverse normal distribution function of real($x$)  \\
int(x) & real &  integer part of $x$, truncated toward zero \\
lgamma(x) & any & $\mbox{lgamma}(\mbox{real}(x))$,  lgamma function of real($x$) \\
log(x) & any & $\log_{e} x$,  natural logarithm (base $e$) of $x$ \\
log10(x) & any & $\log_{10} x$,  logarithm (base $10$) of $x$ \\
norm(x) & any & normal distribution (Gaussian) function of real($x$) \\
rand(x) & any & $\mbox{rand}(\mbox{real}(x))$,  pseudo random number generator \\
real(x) & any &  real part of $x$ \\
sgn(x) & any & 1 if $x>0$, -1 if $x<0$, 0 if $x=0$. imag($x$) ignored \\
sin(x) & any & $\sin x$, sine of $x$ \\
sinh(x) & any & $\sinh x$, hyperbolic sine $x$ in radians \\
sqrt(x) & any & $\sqrt{x}$,  square root of $x$ \\
tan(x) & any & $\tan x$,  tangent of $x$ \\
tanh(x) & any & $\tanh x$, hyperbolic tangent of $x$ in radians\\
\hline
\end{tabular}
\end{center}

A few additional functions are also available.


\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{other {\bf gnuplot} functions} \\ \hline \hline
Function & Arguments & Returns \\ \hline
column(x) & int & column $x$ during datafile manipulation. \\
tm\_hour(x) & int & the hour \\
tm\_mday(x) & int & the day of the month \\
tm\_min(x) & int & the minute \\
tm\_mon(x) & int & the month \\
tm\_sec(x) & int & the second \\
tm\_wday(x) & int & the day of the week \\
tm\_yday(x) & int & the day of the year \\
tm\_year(x) & int & the year \\
valid(x) & int & test validity of $\mbox{column}(x)$ during datafile manip.\\
\hline
\end{tabular}
\end{center}
\subsection{Operators}
The operators in {\bf gnuplot} are the same as the corresponding operators in the
C programming language, except that all operators accept integer, real, and
complex arguments, unless otherwise noted.  The ** operator (exponentiation)
is supported, as in FORTRAN.

Parentheses may be used to change order of evaluation.
\subsubsection{Unary}
The following is a list of all the unary operators and their usages:


\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{Unary Operators}\\ \hline \hline
Symbol & Example & Explanation \\ \hline
\verb@-@ & \verb@-a@ & unary minus \\
\verb@+@ & \verb@+a@ & unary plus (no-operation) \\
\verb@~@ & \verb@~a@ & * one's complement \\
\verb@!@ & \verb@!a@ & * logical negation \\
\verb@!@ & \verb@a!@ & * factorial \\
\verb@$@ & \verb@$3@ & * call arg/column during `using` manipulation \\
\hline
\end{tabular}
\end{center}
(*) Starred explanations indicate that the operator requires an integer
argument.

Operator precedence is the same as in Fortran and C.  As in those languages,
parentheses may be used to change the order of operation.  Thus -2**2 = -4,
but (-2)**2 = 4.

The factorial operator returns a real number to allow a greater range.
\subsubsection{Binary}
The following is a list of all the binary operators and their usages:


\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{Binary Operators} \\ \hline \hline
Symbol & Example & Explanation \\ \hline
\verb~**~ & \verb~a**b~ & exponentiation\\
\verb~*~ & \verb~a*b~ & multiplication\\
\verb~/~ & \verb~a/b~ & division\\
\verb~%~ & \verb~a%b~ & * modulo\\
\verb~+~ & \verb~a+b~ & addition\\
\verb~-~ & \verb~a-b~ & subtraction\\
\verb~==~ & \verb~a==b~ & equality\\
\verb~!=~ & \verb~a!=b~ & inequality\\
\verb~<~ & \verb~a<b~ & less than\\
\verb~<=~ & \verb~a<=b~ & less than or equal to\\
\verb~>~ & \verb~a>b~ & greater than\\
\verb~>=~ & \verb~a>=b~ & greater than or equal to\\
\verb~&~ & \verb~a&b~ & * bitwise AND\\
\verb~^~ & \verb~a^b~ & * bitwise exclusive OR\\
\verb~|~ & \verb~a|b~ & * bitwise inclusive OR\\
\verb~&&~ & \verb~a&&b~ & * logical AND\\
\verb~||~ & \verb~a||b~ & * logical OR\\
\hline
\end{tabular}
\end{center}
(*) Starred explanations indicate that the operator requires integer
arguments.

Logical AND (\&\&) and OR ($|$$|$) short-circuit the way they do in C.  That is,
the second {\bf \&\&} operand is not evaluated if the first is false; the second
{\bf $|$$|$} operand is not evaluated if the first is true.
\subsubsection{Ternary}
There is a single ternary operator:


\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{Ternary Operator} \\ \hline \hline
Symbol & Example & Explanation \\ \hline
\verb~?:~ & \verb~a?b:c~ & ternary operation\\
\hline
\end{tabular}
\end{center}
The ternary operator behaves as it does in C.  The first argument (a), which
must be an integer, is evaluated.  If it is true (non-zero), the second
argument (b) is evaluated and returned; otherwise the third argument (c) is
evaluated and returned.

The ternary operator is very useful both in constructing piecewise functions
and in plotting points only when certain conditions are met.

Examples:

Plot a function that is to equal sin(x) for 0 $<$= x $<$ 1, 1/x for 1 $<$= x $<$ 2,
and undefined elsewhere:
\preverbatim
\begin{verbatim}
     f(x) = 0<=x && x<1 ? sin(x) : 1<=x && x<2 ? 1/x : 1/0
     plot f(x)
\end{verbatim}
\postverbatim
Note that {\bf gnuplot} quietly ignores undefined values, so the final branch of
the function (1/0) will produce no plottable points.  Note also that f(x)
will be plotted as a continuous function across the discontinuity if a line
style is used.  To plot it discontinuously, create separate functions for the
two pieces.  (Parametric functions are also useful for this purpose.)

For data in a file, plot the average of the data in columns 2 and 3 against
the datum in column 1, but only if the datum in column 4 is non-negative:

\preverbatim
\begin{verbatim}
     plot 'file' using 1:( $4<0 ? 1/0 : ($2+$3)/2 )
\end{verbatim}
\postverbatim

Please see {\bf plot data-file using} for an explanation of the {\bf using} syntax.
\subsection{User-defined}
New user-defined variables and functions of one through five variables may
be declared and used anywhere, including on the {\bf plot} command itself.

User-defined function syntax:
\preverbatim
\begin{verbatim}
     <func-name>( <dummy1> {,<dummy2>} ... {,<dummy5>} ) = <expression>
\end{verbatim}
\postverbatim

where $<$expression$>$ is defined in terms of $<$dummy1$>$ through $<$dummy5$>$.

User-defined variable syntax:
\preverbatim
\begin{verbatim}
     <variable-name> = <constant-expression>
\end{verbatim}
\postverbatim

Examples:
\preverbatim
\begin{verbatim}
     w = 2
     q = floor(tan(pi/2 - 0.1))
     f(x) = sin(w*x)
     sinc(x) = sin(pi*x)/(pi*x)
     delta(t) = (t == 0)
     ramp(t) = (t > 0) ? t : 0
     min(a,b) = (a < b) ? a : b
     comb(n,k) = n!/(k!*(n-k)!)
     len3d(x,y,z) = sqrt(x*x+y*y+z*z)
     plot f(x) = sin(x*a), a = 0.2, f(x), a = 0.4, f(x)
\end{verbatim}
\postverbatim

Note that the variable {\bf pi} is already defined.  But it is in no way magic;
you may redefine it to be whatever you like.

Valid names are the same as in most programming languages: they must begin
with a letter, but subsequent characters may be letters, digits, {\tt"}\${\tt"}, or {\tt"}{\tt\_}{\tt"}.
Note, however, that the {\bf fit} mechanism uses several variables with names
that begin {\tt"}FIT{\tt\_}{\tt"}.  It is safest to avoid using such names.  {\tt"}FIT{\tt\_}LIMIT{\tt"},
however, is one that you may wish to redefine. See the documentation
on {\bf fit} for details.


See {\bf show functions}, {\bf show variables}, and {\bf fit}.
\section{Glossary}
Throughout this document an attempt has been made to maintain consistency of
nomenclature.  This cannot be wholly successful because as {\bf gnuplot} has
evolved over time, certain command and keyword names have been adopted that
preclude such perfection.  This section contains explanations of the way
some of these terms are used.

A {\tt"}page{\tt"} or {\tt"}screen{\tt"} is the entire area addressable by {\bf gnuplot}.  On a
monitor, it is the full screen; on a plotter, it is a single sheet of paper.

A screen may contain one or more {\tt"}plots{\tt"}.  A plot is defined by an abscissa
and an ordinate, although these need not actually appear on it, as well as
the margins and any text written therein.

A plot contains one {\tt"}graph{\tt"}.  A graph is defined by an abscissa and an
ordinate, although these need not actually appear on it.

A graph may contain one or more {\tt"}lines{\tt"}.  A line is a single function or
data set.  {\tt"}Line{\tt"} is also a plotting style.  The word will also be used in
sense {\tt"}a line of text{\tt"}.  Presumably the context will remove any ambiguity.

The lines on a graph may have individual names.  These may be listed
together with a sample of the plotting style used to represent them in
the {\tt"}key{\tt"}, sometimes also called the {\tt"}legend{\tt"}.

The word {\tt"}title{\tt"} occurs with multiple meanings in {\bf gnuplot}.  In this
document, it will always be preceded by the adjective {\tt"}plot{\tt"}, {\tt"}line{\tt"}, or
{\tt"}key{\tt"} to differentiate among them.

A graph may have up to four labelled axes.  Various commands have the name of
an axis built into their names, such as {\bf set xlabel}.  Other commands have
one or more axis names as options, such as {\bf set logscale xy}.  The names of
the four axes for these usages are {\tt"}x{\tt"} for the axis along the bottom border
of the plot, {\tt"}y{\tt"} for the left border, {\tt"}x2{\tt"} for the top border, and {\tt"}y2{\tt"} for
the right border.  {\tt"}z{\tt"} also occurs in commands used with 3-d plotting.

When discussing data files, the term {\tt"}record{\tt"} will be resurrected and used
to denote a single line of text in the file, that is, the characters between
newline or end-of-record characters.  A {\tt"}point{\tt"} is the datum extracted from
a single record.  A {\tt"}datablock{\tt"} is a set of points from consecutive records,
delimited by blank records.  A line, when referred to in the context of a
data file, is a subset of a datablock.
\section{Plotting}
There are three {\bf gnuplot} commands which actually create a plot: {\bf plot},
{\bf splot} and {\bf replot}.  {\bf plot} generates 2-d plots, {\bf splot} generates 3-d
plots (actually 2-d projections, of course), and {\bf replot} appends its
arguments to the previous {\bf plot} or {\bf splot} and executes the modified
command.

Much of the general information about plotting can be found in the discussion
of {\bf plot}; information specific to 3-d can be found in the {\bf splot} section.

{\bf plot} operates in either rectangular or polar coordinates -- see {\bf set polar}
for details of the latter.  {\bf splot} operates only in rectangular coordinates,
but the {\bf set mapping} command allows for a few other coordinate systems to be
treated.  In addition, the {\bf using} option allows both {\bf plot} and {\bf splot} to
treat almost any coordinate system you'd care to define.

{\bf splot} can plot surfaces and contours in addition to points and/or lines.
In addition to {\bf splot}, see {\bf set isosamples} for information about defining
the grid for a 3-d function;  {\bf splot datafile} for information about the
requisite file structure for 3-d data values; and {\bf set contour} and {\bf set
cntrparam} for information about contours.
\section{Start-up}
When {\bf gnuplot} is run, it looks for an initialization file to load.  This
file is called {\bf .gnuplot} on Unix and AmigaOS systems, and {\bf GNUPLOT.INI} on
other systems.  If this file is not found in the current directory, the
program will look for it in the home directory (under AmigaOS,
Atari(single)TOS, MS-DOS and OS/2, the environment variable {\bf gnuplot} should
contain the name of this directory).  Note: if NOCWDRC is defined during the
installation, {\bf gnuplot} will not read from the current directory.

If the initialization file is found, {\bf gnuplot} executes the commands in it.
These may be any legal {\bf gnuplot} commands, but typically they are limited to
setting the terminal and defining frequently-used functions or variables.
\section{Substitution}
Command-line substitution is specified by a system command enclosed in
backquotes.  This command is spawned and the output it produces replaces
the name of the command (and backquotes) on the command line.  Some
implementations also support pipes;  see {\bf plot data-file special-filenames}.

Newlines in the output produced by the spawned command are replaced with
blanks.

Command-line substitution can be used anywhere on the {\bf gnuplot} command
line.

Example:

This will run the program {\bf leastsq} and replace {\bf leastsq} (including
backquotes) on the command line with its output:
\preverbatim
\begin{verbatim}
     f(x) = `leastsq`
\end{verbatim}
\postverbatim

or, in VMS
\preverbatim
\begin{verbatim}
     f(x) = `run leastsq`
\end{verbatim}
\postverbatim
\section{Syntax}
The general rules of syntax and punctuation in {\bf gnuplot} are that keywords
and options are order-dependent.  Options and any accompanying parameters are
separated by spaces whereas lists and coordinates are separated by commas.
Ranges are separated by colons and enclosed in brackets [], text and file
names are enclosed in quotes, and a few miscellaneous things are enclosed
in parentheses.  Braces \{\} are used for a few special purposes.

Commas are used to separate coordinates on the {\bf set} commands {\bf arrow},
{\bf key}, and {\bf label}; the list of variables being fitted (the list after the
{\bf via} keyword on the {\bf fit} command); lists of discrete contours or the loop
parameters which specify them on the {\bf set cntrparam} command; the arguments
of the {\bf set} commands {\bf dgrid3d}, {\bf dummy}, {\bf isosamples}, {\bf offsets}, {\bf origin},
{\bf samples}, {\bf size}, {\bf time}, and {\bf view}; lists of tics or the loop parameters
which specify them; the offsets for titles and axis labels; parametric
functions to be used to calculate the x, y, and z coordinates on the {\bf plot},
{\bf replot} and {\bf splot} commands; and the complete sets of keywords specifying
individual plots (data sets or functions) on the {\bf plot}, {\bf replot} and {\bf splot}
commands.

Parentheses are used to delimit sets of explicit tics (as opposed to loop
parameters) and to indicate computations in the {\bf using} filter of the {\bf fit},
{\bf plot}, {\bf replot} and {\bf splot} commands.

(Parentheses and commas are also used as usual in function notation.)

Brackets are used to delimit ranges, whether they are given on {\bf set}, {\bf plot}
or {\bf splot} commands.

Colons are used to separate extrema in {\bf range} specifications (whether they
are given on {\bf set}, {\bf plot} or {\bf splot} commands) and to separate entries in
the {\bf using} filter of the {\bf plot}, {\bf replot}, {\bf splot} and {\bf fit} commands.

Semicolons are used to separate commands given on a single command line.

Braces are used in text to be specially processed by some terminals, like
{\bf postscript}.  They are also used to denote complex numbers: \{3,2\} = 3 + 2i.

Text may be enclosed in single- or double-quotes.  Backslash processing of
sequences like $\backslash$n (newline) and $\backslash$345 (octal character code) is performed for
double-quoted strings, but not for single-quoted strings.

The justification is the same for each line of a multi-line string.  Thus the
center-justified string
\preverbatim
\begin{verbatim}
     "This is the first line of text.\nThis is the second line."
\end{verbatim}
\postverbatim
will produce
\preverbatim
\begin{verbatim}
                      This is the first line of text.
                         This is the second line.
\end{verbatim}
\postverbatim
but
\preverbatim
\begin{verbatim}
     'This is the first line of text.\nThis is the second line.'
\end{verbatim}
\postverbatim
will produce
\preverbatim
\begin{verbatim}
         This is the first line of text.\nThis is the second line.
\end{verbatim}
\postverbatim

Filenames may be entered with either single- or double-quotes.  In this
manual the command examples generally single-quote filenames and double-quote
other string tokens for clarity.

At present you should not embed $\backslash$n inside \{\} when using the enhanced option
of the postscript terminal.

The EEPIC, Imagen, Uniplex, LaTeX, and TPIC drivers allow a newline to be
specified by $\backslash$$\backslash$ in a single-quoted string or $\backslash$$\backslash$$\backslash$$\backslash$ in a double-quoted string.

Back-quotes are used to enclose system commands for substitution.
\section{Time/Date data}
{\bf gnuplot} supports the use of time and/or date information as input data.
This feature is activated by the commands {\bf set xdata time}, {\bf set ydata time},
etc.

Internally all times and dates are converted to the number of seconds from
the year 2000.  The command {\bf set timefmt} defines the format for all inputs:
data files, ranges, tics, label positions --- in short, anything that accepts a
data value must receive it in this format.  Since only one input format can
be in force at a given time, all time/date quantities being input at the same
time must be presented in the same format.  Thus if both x and y data in a
file are time/date, they must be in the same format.

The conversion to and from seconds assumes Universal Time (which is the same
as Greenwich Standard Time).  There is no provision for changing the time
zone or for daylight savings.  If all your data refer to the same time zone
(and are all either daylight or standard) you don't need to worry about these
things.  But if the absolute time is crucial for your application, you'll
need to convert to UT yourself.

Commands like {\bf show xrange} will re-interpret the integer according to
{\bf timefmt}.  If you change {\bf timefmt}, and then {\bf show} the quantity again, it
will be displayed in the new {\bf timefmt}.  For that matter, if you give the
deactivation command (like {\bf set xdata}), the quantity will be shown in its
numerical form.

The command {\bf set format} defines the format that will be used for tic labels,
whether or not the specified axis is time/date.

If time/date information is to be plotted from a file, the {\bf using} option
{\em must\/} be used on the {\bf plot} or {\bf splot} command.  These commands simply use
white space to separate columns, but white space may be embedded within the
time/date string.  If you use tabs as a separator, some trial-and-error may
be necessary to discover how your system treats them.

The following example demonstrates time/date plotting.

Suppose the file {\tt"}data{\tt"} contains records like

\preverbatim
\begin{verbatim}
     03/21/95 10:00  6.02e23
\end{verbatim}
\postverbatim

This file can be plotted by

\preverbatim
\begin{verbatim}
     set xdata time
     set timefmt "%m/%d/%y"
     set xrange ["03/21/95":"03/22/95"]
     set format x "%m/%d"
     set timefmt "%m/%d/%y %H:%M"
     plot "data" using 1:3
\end{verbatim}
\postverbatim

which will produce xtic labels that look like {\tt"}03/21{\tt"}.

See the descriptions of each command for more details.
\part{Commands}
This section lists the commands acceptable to {\bf gnuplot} in alphabetical
order.  Printed versions of this document contain all commands; on-line
versions may not be complete.  Indeed, on some systems there may be no
commands at all listed under this heading.

Note that in most cases unambiguous abbreviations for command names and their
options are permissible, i.e., {\tt"}{\bf p f(x) w l}{\tt"} instead of {\tt"}{\bf plot f(x) with
lines}{\tt"}.

In the syntax descriptions, braces (\{\}) denote optional arguments and a
vertical bar ($|$) separates mutually exclusive choices.
\section{Cd}
The {\bf cd} command changes the working directory.

Syntax:
\preverbatim
\begin{verbatim}
     cd '<directory-name>'
\end{verbatim}
\postverbatim

The directory name must be enclosed in quotes.

Examples:
\preverbatim
\begin{verbatim}
     cd 'subdir'
     cd ".."
\end{verbatim}
\postverbatim

DOS users {\em must\/} use single-quotes --- backslash [$\backslash$] has special significance
inside double-quotes.  For example,
\preverbatim
\begin{verbatim}
     cd "c:\newdata"
\end{verbatim}
\postverbatim
fails, but
\preverbatim
\begin{verbatim}
     cd 'c:\newdata'
\end{verbatim}
\postverbatim
works as expected.
\section{Call}
The {\bf call} command is identical to the load command with one exception: you
can have up to ten additional parameters to the command (delimited according
to the standard parser rules) which can be substituted into the lines read
from the file.  As each line is read from the {\bf call}ed input file, it is
scanned for the sequence {\bf \$} (dollar-sign) followed by a digit (0--9).  If
found, the sequence is replaced by the corresponding parameter from the
{\bf call} command line.  If the parameter was specified as a string in the
{\bf call} line, it is substituted without its enclosing quotes.  {\bf \$} followed by
any character other than a digit will be that character.  E.g. use {\bf \$\$} to
get a single {\bf \$}.  Providing more than ten parameters on the {\bf call} command
line will cause an error.  A parameter that was not provided substitutes as
nothing.  Files being {\bf call}ed may themselves contain {\bf call} or {\bf load}
commands.

The {\bf call} command {\em must\/} be the last command on a multi-command line.

Syntax:
\preverbatim
\begin{verbatim}
     call "<input-file>" <parameter-0> <parm-1> ... <parm-9>
\end{verbatim}
\postverbatim

The name of the input file must be enclosed in quotes, and it is recommended
that parameters are similarly enclosed in quotes (future versions of gnuplot
may treat quoted and unquoted arguments differently).

Example:

If the file 'calltest.gp' contains the line:
\preverbatim
\begin{verbatim}
     print "p0=$0 p1=$1 p2=$2 p3=$3 p4=$4 p5=$5 p6=$6 p7=x$7x"
\end{verbatim}
\postverbatim

entering the command:
\preverbatim
\begin{verbatim}
     call 'calltest.gp' "abcd" 1.2 + "'quoted'" -- "$2"
\end{verbatim}
\postverbatim

will display:
\preverbatim
\begin{verbatim}
     p0=abcd p1=1.2 p2=+ p3='quoted' p4=- p5=- p6=$2 p7=xx
\end{verbatim}
\postverbatim

NOTE: there is a clash in syntax with the datafile {\bf using} callback
operator.  Use {\bf \$\$n} or {\bf column(n)} to access column n from a datafile inside
a {\bf call}ed datafile plot.
\section{Clear}
The {\bf clear} command erases the current screen or output device as specified
by {\bf set output}.  This usually generates a formfeed on hardcopy devices.  Use
{\bf set terminal} to set the device type.

For some terminals {\bf clear} erases only the portion of the plotting surface
defined by {\bf set size}, so for these it can be used in conjunction with {\bf set
multiplot} to create an inset.

Example:
\preverbatim
\begin{verbatim}
     set multiplot
     plot sin(x)
     set origin 0.5,0.5
     set size 0.4,0.4
     clear
     plot cos(x)
     set nomultiplot
\end{verbatim}
\postverbatim

Please see {\bf set multiplot}, {\bf set size}, and {\bf set origin} for details of these
commands.
\section{Exit}
The commands {\bf exit} and {\bf quit} and the END-OF-FILE character will exit the
current {\bf gnuplot} command file and {\bf load} the next one.  See {\tt"}help
batch/interactive{\tt"} for more details.

Each of these commands will clear the output device (as does the {\bf clear}
command) before exiting.
\section{Fit}
The {\bf fit} command can fit a user-defined function to a set of data points
(x,y) or (x,y,z), using an implementation of the nonlinear least-squares
(NLLS) Marquardt-Levenberg algorithm.  Any user-defined variable occurring in
the function body may serve as a fit parameter, but the return type of the
function must be real.

Syntax:
\preverbatim
\begin{verbatim}
     fit {[xrange] {[yrange]}} <function> '<datafile>'
         {datafile-modifiers}
         via '<parameter file>' | <var1>{,<var2>,...}
\end{verbatim}
\postverbatim

Ranges may be specified to temporarily limit the data which is to be fitted;
any out-of-range data points are ignored. The syntax is
\preverbatim
\begin{verbatim}
     [{dummy_variable=}{<min>}{:<max>}],
\end{verbatim}
\postverbatim
analogous to {\bf plot}; see {\bf plot ranges}.

$<$function$>$ is any valid {\bf gnuplot} expression, although it is usual to use a
previously user-defined function of the form f(x) or f(x,y).

$<$datafile$>$ is treated as in the {\bf plot} command.  All the {\bf plot datafile}
modifiers ({\bf using}, {\bf every},...) except {\bf smooth} are applicable to {\bf fit}.
See {\bf plot datafile}.

The default data formats for fitting functions with a single independent
variable, y=f(x), are \{x:\}y or x:y:s; those formats can be changed with
the datafile {\bf using} qualifier.  The third item, (a column number or an
expression), if present, is interpreted as the standard deviation of the
corresponding y value and is used to compute a weight for the datum, 1/s**2.
Otherwise, all data points are weighted equally, with a weight of one.

To fit a function with two independent variables, z=f(x,y), the required
format is {\bf using} with four items, x:y:z:s.  The complete format must be
given --- no default columns are assumed for a missing token.  Weights for
each data point are evaluated from 's' as above.  If error estimates are
not available, a constant value can be specified as a constant expression
(see {\bf plot datafile using}), e.g., {\bf using 1:2:3:(1)}.

Multiple datasets may be simultaneously fit with functions of one
independent variable by making y a 'pseudo-variable', e.g., the dataline
number, and fitting as two independent variables.  See {\bf fit multibranch}.

The {\bf via} qualifier specifies which parameters are to be adjusted, either
directly, or by referencing a parameter file.

Examples:
\preverbatim
\begin{verbatim}
     f(x) = a*x**2 + b*x + c
     g(x,y) = a*x**2 + b*y**2 + c*x*y
     FIT_LIMIT = 1e-6
     fit f(x) 'measured.dat' via 'start.par'
     fit f(x) 'measured.dat' using 3:($7-5) via 'start.par'
     fit f(x) './data/trash.dat' using 1:2:3 via a, b, c
     fit g(x,y) 'surface.dat' using 1:2:3:(1) via a, b, c
\end{verbatim}
\postverbatim

After each iteration step, detailed information about the current state
of the fit is written to the display.  The same information about the
initial and final states is written to a log file, {\tt"}fit.log{\tt"}.  This file
is always appended to, so as to not lose any previous fit history;  it
should be deleted or renamed as desired.

The fit may be interrupted by pressing Ctrl-C (any key but Ctrl-C under
MSDOS and Atari Multitasking Systems).  After the current iteration
completes, you have the option to (1) stop the fit and accept the current
parameter values, (2) continue the fit, (3) execute a {\bf gnuplot} command
as specified by the environment variable FIT{\tt\_}SCRIPT.  The default for
FIT{\tt\_}SCRIPT is {\bf replot}, so if you had previously plotted both the data
and the fitting function in one graph, you can display the current state
of the fit.

Once {\bf fit} has finished, the {\bf update} command may be used to store final
values in a file for subsequent use as a parameter file.   See {\bf update}
for details.
\subsection{Adjustable parameters}
There are two ways that {\bf via} can specify the parameters to be adjusted,
either directly on the command line or indirectly, by referencing a
parameter file.  The two use different means to set initial values.

Adjustable parameters can be specified by a comma-separated list of variable
names after the {\bf via} keyword.  Any variable that is not already defined is
is created with an initial value of 1.0.  However, the fit is more likely
to converge rapidly if the variables have been previously declared with more
appropriate starting values.

In a parameter file, each parameter to be varied and a corresponding initial
value are specified, one per line, in the form
\preverbatim
\begin{verbatim}
     varname = value
\end{verbatim}
\postverbatim

Comments, marked by '\#', and blank lines are permissible.  The
special form
\preverbatim
\begin{verbatim}
     varname = value       # FIXED
\end{verbatim}
\postverbatim

means that the variable is treated as a 'fixed parameter', initialized by the
parameter file, but not adjusted by {\bf fit}.  For clarity, it may be useful to
designate variables as fixed parameters so that their values are reported by
{\bf fit}.  The keyword {\bf \# FIXED} has to appear in exactly this form.

\subsection{Beginner's guide}
{\bf fit} is used to find a set of parameters that 'best' fits your data to your
user-defined function.  The fit is judged on the basis of the the sum of the
squared differences or 'residuals' (SSR) between the input data points and
the function values, evaluated at the same places.  This quantity is often
called 'chisquare' (i.e., the Greek letter chi, to the power of 2).  The
algorithm attempts to minimize SSR, or more precisely, WSSR, as the residuals
are 'weighted' by the input data errors (or 1.0) before being squared; see
{\bf fit error{\tt\_}estimates} for details.

That's why it is called 'least-squares fitting'.  Let's look at an example
to see what is meant by 'non-linear', but first we had better go over some
terms.  Here it is convenient to use z as the dependent variable for
user-defined functions of either one independent variable, z=f(x), or two
independent variables, z=f(x,y).  A parameter is a user-defined variable
that {\bf fit} will adjust, i.e., an unknown quantity in the function
declaration.  Linearity/non-linearity refers to the relationship of the
dependent variable, z, to the parameters which {\bf fit} is adjusting, not of
z to the independent variables, x and/or y.  (To be technical, the
second \{and higher\} derivatives of the fitting function with respect to
the parameters are zero for a linear least-squares problem).

For linear least-squares (LLS), the user-defined function will be a sum of
simple functions, not involving any parameters, each multiplied by one
parameter.  NLLS handles more complicated functions in which parameters can
be used in a large number of ways.  An example that illustrates the
difference between linear and nonlinear least-squares is the Fourier series.
One member may be written as
\preverbatim
\begin{verbatim}
    z=a*sin(c*x) + b*cos(c*x).
\end{verbatim}
\postverbatim
If a and b are the unknown parameters and c is constant, then estimating
values of the parameters is a linear least-squares problem.  However, if
c is an unknown parameter, the problem is nonlinear.

In the linear case, parameter values can be determined by comparatively
simple linear algebra, in one direct step.  However LLS is a special case
which is also solved along with more general NLLS problems by the iterative
procedure that {\bf gnuplot} uses.  {\bf fit} attempts to find the minimum by doing
a search.  Each step (iteration) calculates WSSR with a new set of parameter
values.  The Marquardt-Levenberg algorithm selects the parameter values for
the next iteration.  The process continues until a preset criterium is met,
either (1) the fit has {\tt"}converged{\tt"} (the relative change in WSSR is less than
FIT{\tt\_}LIMIT), or (2) it reaches a preset iteration count limit, FIT{\tt\_}MAXITER
(see {\bf fit control variables}).  The fit may also be interrupted
and subsequently halted from the keyboard (see {\bf fit}).

Often the function to be fitted will be based on a model (or theory) that
attempts to describe or predict the behaviour of the data.  Then {\bf fit} can
be used to find values for the free parameters of the model, to determine
how well the data fits the model, and to estimate an error range for each
parameter.  See {\bf fit error{\tt\_}estimates}.

Alternatively, in curve-fitting, functions are selected independent of
a model (on the basis of experience as to which are likely to describe
the trend of the data with the desired resolution and a minimum number
of parameters*functions.)  The {\bf fit} solution then provides an analytic
representation of the curve.

However, if all you really want is a smooth curve through your data points,
the {\bf smooth} option to {\bf plot} may be what you've been looking for rather
than {\bf fit}.
\subsection{Error estimates}
In {\bf fit}, the term {\tt"}error{\tt"} is used in two different contexts, data error
estimates and parameter error estimates.

Data error estimates are used to calculate the relative weight of each data
point when determining the weighted sum of squared residuals, WSSR or
chisquare.  They can affect the parameter estimates, since they determine
how much influence the deviation of each data point from the fitted function
has on the final values.  Some of the {\bf fit} output information, including
the parameter error estimates, is more meaningful if accurate data error
estimates have been provided.

The 'statistical overview' describes some of the {\bf fit} output and gives some
background for the 'practical guidelines'.
\subsubsection{Statistical overview}
The theory of non-linear least-squares (NLLS) is generally described in terms
of a normal distribution of errors, that is, the input data is assumed to be
a sample from a population having a given mean and a Gaussian (normal)
distribution about the mean with a given standard deviation.  For a sample of
sufficiently large size, and knowing the population standard deviation, one
can use the statistics of the chisquare distribution to describe a {\tt"}goodness
of fit{\tt"} by looking at the variable often called {\tt"}chisquare{\tt"}.  Here, it is
sufficient to say that a reduced chisquare (chisquare/degrees of freedom,
where degrees of freedom is the number of datapoints less the number of
parameters being fitted) of 1.0 is an indication that the weighted sum of
squared deviations between the fitted function and the data points is the
same as that expected for a random sample from a population characterized by
the function with the current value of the parameters and the given standard
deviations.

If the standard deviation for the population is not constant, as in counting
statistics where variance = counts, then each point should be individually
weighted when comparing the observed sum of deviations and the expected sum
of deviations.

At the conclusion {\bf fit} reports 'stdfit', the standard deviation of the fit,
which is the rms of the residuals, and the variance of the residuals, also
called 'reduced chisquare' when the data points are weighted.  The number of
degrees of freedom (the number of data points minus the number of fitted
parameters) is used in these estimates because the parameters used in
calculating the residuals of the datapoints were obtained from the same data.

To estimate confidence levels for the parameters, one can use the minimum
chisquare obtained from the fit and chisquare statistics to determine the
value of chisquare corresponding to the desired confidence level, but
considerably more calculation is required to determine the combinations of
parameters which produce such values.

Rather than determine confidence intervals, {\bf fit} reports parameter error
estimates which are readily obtained from the variance-covariance matrix
after the final iteration.  By convention, these estimates are called
{\tt"}standard errors{\tt"} or {\tt"}asymptotic standard errors{\tt"}, since they are calculated
in the same way as the standard errors (standard deviation of each parameter)
of a linear least-squares problem, even though the statistical conditions for
designating the quantity calculated to be a standard deviation are not
generally valid for the NLLS problem.  The asymptotic standard errors are
generally over-optimistic and should not be used for determining confidence
levels, but are useful for qualitative purposes.

The final solution also produces a correlation matrix, which gives an
indication of the correlation of parameters in the region of the solution;
if one parameter is changed, increasing chisquare, does changing another
compensate?  The main diagonal elements, autocorrelation, are all 1; if
all parameters were independent, all other elements would be nearly 0.  Two
variables which completely compensate each other would have an off-diagonal
element of unit magnitude, with a sign depending on whether the relation is
proportional or inversely proportional.  The smaller the magnitudes of the
off-diagonal elements, the closer the estimates of the standard deviation
of each parameter would be to the asymptotic standard error.
\subsubsection{Practical guidelines}
If you have a basis for assigning weights to each data point, doing so lets
you make use of additional knowledge about your measurements, e.g., take into
account that some points may be more reliable than others.  That may affect
the final values of the parameters.

Weighting the data provides a basis for interpreting the additional {\bf fit}
output after the last iteration.  Even if you weight each point equally,
estimating an average standard deviation rather than using a weight of 1
makes WSSR a dimensionless variable, as chisquare is by definition.

Each fit iteration will display information which can be used to evaluate
the progress of the fit.  (An '*' indicates that it did not find a smaller
WSSR and is trying again.)  The 'sum of squares of residuals', also called
'chisquare', is the WSSR between the data and your fitted function; {\bf fit}
has minimized that.  At this stage, with weighted data, chisquare is expected
to approach the number of degrees of freedom (data points minus parameters).
The WSSR can be used to calculate the reduced chisquare (WSSR/ndf) or stdfit,
the standard deviation of the fit, sqrt(WSSR/ndf).  Both of these are
reported for the final WSSR.

If the data are unweighted, stdfit is the rms value of the deviation of the
data from the fitted function, in user units.

If you supplied valid data errors, the number of data points is large enough,
and the model is correct, the reduced chisquare should be about unity.  (For
details, look up the 'chi-squared distribution' in your favourite statistics
reference.)  If so, there are additional tests, beyond the scope of this
overview, for determining how well the model fits the data.

A reduced chisquare much larger than 1.0 may be due to incorrect data error
estimates, data errors not normally distributed, systematic measurement
errors, 'outliers', or an incorrect model function.  A plot of the residuals,
e.g., {\bf plot 'datafile' using 1:(\$2-f(\$1))}, may help to show any systematic
trends.  Plotting both the data points and the function may help to suggest
another model.

Similarly, a reduced chisquare less than 1.0 indicates WSSR is less than that
expected for a random sample from the function with normally distributed
errors.  The data error estimates may be too large, the statistical
assumptions may not be justified, or the model function may be too general,
fitting fluctuations in a particular sample in addition to the underlying
trends.  In the latter case, a simpler function may be more appropriate.

You'll have to get used to both {\bf fit} and the kind of problems you apply it
to before you can relate the standard errors to some more practical estimates
of parameter uncertainties or evaluate the significance of the correlation
matrix.

Note that {\bf fit}, in common with most NLLS implementations, minimizes the
weighted sum of squared distances (y-f(x))**2.  It does not provide any means
to account for {\tt"}errors{\tt"} in the values of x, only in y.  Also, any {\tt"}outliers{\tt"}
(data points outside the normal distribution of the model) will have an
exaggerated effect on the solution.
\subsection{Fit controlling}
There are a number of {\bf gnuplot} variables that can be defined to affect
{\bf fit}.  Those which can be defined once {\bf gnuplot} is running are listed
under 'control{\tt\_}variables' while those defined before starting {\bf gnuplot}
are listed under 'environment{\tt\_}variables'.
\subsubsection{Control variables}
The default epsilon limit (1e-5) may be changed by declaring a value for
\preverbatim
\begin{verbatim}
     FIT_LIMIT
\end{verbatim}
\postverbatim
When the sum of squared residuals changes between two iteration steps by
a factor less than this number (epsilon), the fit is considered to have
'converged'.

The maximum number of iterations may be limited by declaring a value for
\preverbatim
\begin{verbatim}
     FIT_MAXITER
\end{verbatim}
\postverbatim
A value of 0 (or not defining it at all)  means that there is no limit.

If you need even more control about the algorithm, and know the
Marquardt-Levenberg algorithm well, there are some more variables to
influence it. The startup value of {\bf lambda} is normally calculated
automatically from the ML-matrix, but if you want to, you may provide
your own one with
\preverbatim
\begin{verbatim}
     FIT_START_LAMBDA
\end{verbatim}
\postverbatim
Specifying FIT{\tt\_}START{\tt\_}LAMBDA as zero or less will re-enable the automatic
selection. The variable
\preverbatim
\begin{verbatim}
     FIT_LAMBDA_FACTOR
\end{verbatim}
\postverbatim
gives the factor by which {\bf lambda} is increased or decreased whenever
the chi-squared target function increased or decreased significantly.
Setting FIT{\tt\_}LAMBDA{\tt\_}FACTOR to zero re-enables the default factor of
10.0.

Oher variables with the FIT{\tt\_} prefix may be added to {\bf fit}, so it is safer
not to use that prefix for user-defined variables.

The variables FIT{\tt\_}SKIP and FIT{\tt\_}INDEX were used by earlier releases of
{\bf gnuplot} with a 'fit' patch called {\bf gnufit} and are no longer available.
The datafile {\bf every} modifier provides the functionality of FIT{\tt\_}SKIP.
FIT{\tt\_}INDEX was used for multi-branch fitting, but multi-branch fitting of
one independent variable is now done as a pseudo-3D fit in which the
second independent variable and {\bf using} are used to specify the branch.
See {\bf fit multi-branch}.
\subsubsection{Environment variables}
The environment variables must be defined before {\bf gnuplot} is executed; how
to do so depends on your operating system.

\preverbatim
\begin{verbatim}
     FIT_LOG
\end{verbatim}
\postverbatim
changes the name (and/or path) of the file to which the fit log will be
written from the default of {\tt"}fit.log{\tt"} in the working directory.

\preverbatim
\begin{verbatim}
     FIT_SCRIPT
\end{verbatim}
\postverbatim
specifies a command that may be executed after an user interrupt. The default
is {\bf replot}, but a {\bf plot} or {\bf load} command may be useful to display a plot
customized to highlight the progress of the fit.
\subsection{Multi-branch}
In multi-branch fitting, multiple data sets can be simultaneously fit with
functions of one independent variable having common parameters by minimizing
the total WSSR.  The function and parameters (branch) for each data set are
selected by using a 'pseudo-variable', e.g., either the dataline number (a
'column' index of -1) or the datafile index (-2), as the second independent
variable.

Example:  Given two exponential decays of the form, z=f(x), each describing
a different data set but having a common decay time, estimate the values of
the parameters.  If the datafile has the format x:z:s, then
\preverbatim
\begin{verbatim}
    f(x,y) = (y==0) ? a*exp(-x/tau) : b*exp(-x/tau)
    fit f(x,y) 'datafile' using  1:-1:2:3  via a, b, tau
\end{verbatim}
\postverbatim

For a more complicated example, see the file {\tt"}hexa.fnc{\tt"} used by the
{\tt"}fit.dem{\tt"} demo.

Appropriate weighting may be required since unit weights may cause one
branch to predominate if there is a difference in the scale of the dependent
variable.  Fitting each branch separately, using the multi-branch solution
as initial values, may give an indication as to the relative effect of each
branch on the joint solution.
\subsection{Starting values}
Nonlinear fitting is not guaranteed to converge to the global optimum (the
solution with the smallest sum of squared residuals, SSR), and can get stuck
at a local minimum.  The routine has no way to determine that;  it is up to
you to judge whether this has happened.

{\bf fit} may, and often will get {\tt"}lost{\tt"} if started far from a solution, where
SSR is large and changing slowly as the parameters are varied, or it may
reach a numerically unstable region (e.g., too large a number causing a
floating point overflow) which results in an {\tt"}undefined value{\tt"} message
or {\bf gnuplot} halting.

To improve the chances of finding the global optimum, you should set the
starting values at least roughly in the vicinity of the solution, e.g.,
within an order of magnitude, if possible.  The closer your starting values
are to the solution, the less chance of stopping at another minimum.  One way
to find starting values is to plot data and the fitting function on the same
graph and change parameter values and {\bf replot} until reasonable similarity
is reached.  The same plot is also useful to check whether the fit stopped at
a minimum with a poor fit.

Of course, a reasonably good fit is not proof there is not a {\tt"}better{\tt"} fit (in
either a statistical sense, characterized by an improved goodness-of-fit
criterion, or a physical sense, with a solution more consistent with the
model.)  Depending on the problem, it may be desirable to {\bf fit} with various
sets of starting values, covering a reasonable range for each parameter.
\subsection{Tips}
Here are some tips to keep in mind to get the most out of {\bf fit}.  They're not
very organized, so you'll have to read them several times until their essence
has sunk in.

The two forms of the {\bf via} argument to {\bf fit} serve two largely distinct
purposes.  The {\bf via {\tt"}file{\tt"}} form is best used for (possibly unattended) batch
operation, where you just supply the startup values in a file and can later
use {\bf update} to copy the results back into another (or the same) parameter
file.

The {\bf via var1, var2, ...} form is best used interactively, where the command
history mechanism may be used to edit the list of parameters to be fitted or
to supply new startup values for the next try.  This is particularly useful
for hard problems, where a direct fit to all parameters at once won't work
without good starting values.  To find such, you can iterate several times,
fitting only some of the parameters, until the values are close enough to the
goal that the final fit to all parameters at once will work.

Make sure that there is no mutual dependency among parameters of the function
you are fitting.  For example, don't try to fit a*exp(x+b), because
a*exp(x+b)=a*exp(b)*exp(x).  Instead, fit either a*exp(x) or exp(x+b).

A technical issue:  the parameters must not be too different in magnitude.
The larger the ratio of the largest and the smallest absolute parameter
values, the slower the fit will converge.  If the ratio is close to or above
the inverse of the machine floating point precision, it may take next to
forever to converge, or refuse to converge at all.  You will have to adapt
your function to avoid this, e.g., replace 'parameter' by '1e9*parameter' in
the function definition, and divide the starting value by 1e9.

If you can write your function as a linear combination of simple functions
weighted by the parameters to be fitted, by all means do so.  That helps a
lot, because the problem is no longer nonlinear and should converge with only
a small number of iterations, perhaps just one.

Some prescriptions for analysing data, given in practical experimentation
courses, may have you first fit some functions to your data, perhaps in a
multi-step process of accounting for several aspects of the underlying
theory one by one, and then extract the information you really wanted from
the fitting parameters of those functions.  With {\bf fit}, this may often be
done in one step by writing the model function directly in terms of the
desired parameters.  Transforming data can also quite often be avoided,
though sometimes at the cost of a more difficult fit problem.  If you think
this contradicts the previous paragraph about simplifying the fit function,
you are correct.

A {\tt"}singular matrix{\tt"} message indicates that this implementation of the
Marquardt-Levenberg algorithm can't calculate parameter values for the next
iteration.  Try different starting values, writing the function in another
form, or a simpler function.

Finally, a nice quote from the manual of another fitting package (fudgit),
that kind of summarizes all these issues:  {\tt"}Nonlinear fitting is an art!{\tt"}
\section{Help}
The {\bf help} command displays on-line help. To specify information on a
particular topic use the syntax:

\preverbatim
\begin{verbatim}
     help {<topic>}
\end{verbatim}
\postverbatim

If $<$topic$>$ is not specified, a short message is printed about {\bf gnuplot}.
After help for the requested topic is given, a menu of subtopics is given;
help for a subtopic may be requested by typing its name, extending the help
request.  After that subtopic has been printed, the request may be extended
again or you may go back one level to the previous topic.  Eventually, the
{\bf gnuplot} command line will return.

If a question mark (?) is given as the topic, the list of topics currently
available is printed on the screen.
\section{If}
The {\bf if} command allows commands to be executed conditionally.

Syntax:
\preverbatim
\begin{verbatim}
     if (<condition>) <command-line>
\end{verbatim}
\postverbatim

$<$condition$>$ will be evaluated.  If it is true (non-zero), then the command(s)
of the $<$command-line$>$ will be executed.  If $<$condition$>$ is false (zero), then
the entire $<$command-line$>$ is ignored.  Note that use of {\bf ;} to allow multiple
commands on the same line will {\em not\/} end the conditionalized commands.

Examples:
\preverbatim
\begin{verbatim}
     pi=3
     if (pi!=acos(-1)) print "?Fixing pi!"; pi=acos(-1); print pi
\end{verbatim}
\postverbatim
will display:
\preverbatim
\begin{verbatim}
     ?Fixing pi!
     3.14159265358979
\end{verbatim}
\postverbatim
but
\preverbatim
\begin{verbatim}
     if (1==2) print "Never see this"; print "Or this either"
\end{verbatim}
\postverbatim
will not display anything.

See {\bf reread} for an example of how {\bf if} and {\bf reread} can be used together to
perform a loop.
\section{Load}
The {\bf load} command executes each line of the specified input file as if it
had been typed in interactively.  Files created by the {\bf save} command can
later be {\bf load}ed.  Any text file containing valid commands can be created
and then executed by the {\bf load} command.  Files being {\bf load}ed may themselves
contain {\bf load} or {\bf call} commands.  See {\bf comment} for information about
comments in commands.  To {\bf load} with arguments, see {\bf call}.

The {\bf load} command {\em must\/} be the last command on a multi-command line.

Syntax:
\preverbatim
\begin{verbatim}
     load "<input-file>"
\end{verbatim}
\postverbatim

The name of the input file must be enclosed in quotes.

The special filename {\tt"}-{\tt"} may be used to {\bf load} commands from standard input.
This allows a {\bf gnuplot} command file to accept some commands from standard
input.  Please see {\tt"}help batch/interactive{\tt"} for more details.

Examples:
\preverbatim
\begin{verbatim}
     load 'work.gnu'
     load "func.dat"
\end{verbatim}
\postverbatim

The {\bf load} command is performed implicitly on any file names given as
arguments to {\bf gnuplot}.  These are loaded in the order specified, and
then {\bf gnuplot} exits.
\section{Pause}
The {\bf pause} command displays any text associated with the command and then
waits a specified amount of time or until the carriage return is pressed.
{\bf pause} is especially useful in conjunction with {\bf load} files.

Syntax:
\preverbatim
\begin{verbatim}
     pause <time> {"<string>"}
\end{verbatim}
\postverbatim

$<$time$>$ may be any integer constant or expression.  Choosing -1 will wait
until a carriage return is hit, zero (0) won't pause at all, and a positive
integer will wait the specified number of seconds.  {\bf pause 0} is synonymous
with {\bf print}.

Note: Since {\bf pause} communicates with the operating system rather than the
graphics, it may behave differently with different device drivers (depending
upon how text and graphics are mixed).

Examples:
\preverbatim
\begin{verbatim}
     pause -1    # Wait until a carriage return is hit
     pause 3     # Wait three seconds
     pause -1  "Hit return to continue"
     pause 10  "Isn't this pretty?  It's a cubic spline."
\end{verbatim}
\postverbatim

\section{Plot}
{\bf plot} is the primary command for drawing plots with {\bf gnuplot}.  It creates
plots of functions and data in many, many ways.  {\bf plot} is used to draw 2-d
functions and data; {\bf splot} draws 2-d projections of 3-d surfaces and data.
{\bf plot} and {\bf splot} contain many common features; see {\bf splot} for differences.
Note specifically that {\bf splot}'s {\bf binary} and {\bf matrix} options do not exist
for {\bf plot}.

Syntax:
\preverbatim
\begin{verbatim}
     plot {<ranges>}
          {<function> | {"<datafile>" {datafile-modifiers}}}
          {axes <axes>} {<title-spec>} {with <style>}
          {, {definitions,} <function> ...}
\end{verbatim}
\postverbatim

where either a $<$function$>$ or the name of a data file enclosed in quotes is
supplied.  A function is a mathematical expression or a pair of mathematical
expressions in parametric mode.  The expressions may be defined completely or
in part earlier in the stream of {\bf gnuplot} commands (see {\bf user-defined}).

It is also possible to define functions and parameters on the {\bf plot} command
itself.  This is done merely by isolating them from other items with commas.

There are four possible sets of axes available; the keyword $<$axes$>$ is used to
select the axes for which a particular line should be scaled.  {\bf x1y1} refers
to the axes on the bottom and left; {\bf x2y2} to those on the top and right;
{\bf x1y2} to those on the bottom and right; and {\bf x2y1} to those on the top and
left.  Ranges specified on the {\bf plot} command apply only to the first set of
axes (bottom left).

Examples:
\preverbatim
\begin{verbatim}
     plot sin(x)
     plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)
     plot [t=1:10] [-pi:pi*2] tan(t), \
          "data.1" using (tan($2)):($3/$4) smooth csplines \
                   axes x1y2 notitle with lines 5
\end{verbatim}
\postverbatim

\subsection{Data-file}
Discrete data contained in a file can be displayed by specifying the name of
the data file (enclosed in single or double quotes) on the {\bf plot} command line.

Syntax:
\preverbatim
\begin{verbatim}
     plot '<file_name>' {index <index list>}
                           {every <every list>}
                           {thru <thru expression>}
                           {using <using list>}
                           {smooth <option>}
\end{verbatim}
\postverbatim

The modifiers {\bf index}, {\bf every}, {\bf thru}, {\bf using}, and {\bf smooth} are discussed
separately.  In brief, {\bf index} selects which data sets in a multi-data-set
file are to be plotted, {\bf every} specifies which points within a single data
set are to be plotted, {\bf using} determines how the columns within a single
record are to be interpreted ({\bf thru} is a special case of {\bf using}), and
{\bf smooth} allows for simple interpolation and approximation.  ('splot' has a
similar syntax, but does not support the {\bf smooth} and {\bf thru} options.)

Data files should contain at least one data point per record ({\bf using} can
select one data point from the record).  Records beginning with {\bf \#} (and
also with {\bf !} on VMS) will be treated as comments and ignored.  Each data
point represents an (x,y) pair.  For {\bf plot}s with error bars (see {\bf set style
errorbars}), each data point is (x,y,ydelta), (x,y,ylow,yhigh), (x,y,xdelta),
(x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh).  In all cases, the numbers
on each record of a data file must be separated by white space (one or more
blanks or tabs), unless a format specifier is provided by the {\bf using} option.
This white space divides each record into columns.

Data may be written in exponential format with the exponent preceded by the
letter e, E, d, D, q, or Q.

Only one column (the y value) need be provided.  If x is omitted, {\bf gnuplot}
provides integer values starting at 0.

In datafiles, blank records (records with no characters other than blanks and
a newline and/or carriage return) are significant --- pairs of blank records
separate {\bf index}es (see {\bf plot datafile index}).  Data separated by double
blank records are treated as if they were in separate data files.

Single blank records designate discontinuities in a {\bf plot}; no line will join
points separated by a blank records (if they are plotted with a line style).

If autoscaling has been enabled ({\bf set autoscale}), the axes are automatically
extended to include all datapoints, with a whole number of tic marks if tics
are being drawn.  This has two consequences: i) For {\bf splot}, the corner of
the surface may not coincide with the corner of the base.  In this case, no
vertical line is drawn.  ii) When plotting data with the same x range on a
dual-axis graph, the x coordinates may not coincide if the x2tics are not
being drawn.  This is because the x axis has been autoextended to a whole
number of tics, but the x2 axis has not.  The following example illustrates
the problem:

\preverbatim
\begin{verbatim}
     reset; plot '-', '-'
     1 1
     19 19
     e
     1 1
     19 19
     e
\end{verbatim}
\postverbatim
\subsubsection{Every}
The {\bf every} keyword allows a periodic sampling of a data set to be plotted.

In the discussion a {\tt"}point{\tt"} is a datum defined by a single record in the
file; {\tt"}block{\tt"} here will mean the same thing as {\tt"}datablock{\tt"} (see {\bf glossary}).

Syntax:
\preverbatim
\begin{verbatim}
     plot 'file' every {<point_incr>}
                         {:{<block_incr>}
                           {:{<start_point>}
                             {:{<start_block>}
                               {:{<end_point>}
                                 {:<end_block>}}}}}
\end{verbatim}
\postverbatim

The data points to be plotted are selected according to a loop from
$<${\bf start{\tt\_}point}$>$ to $<${\bf end{\tt\_}point}$>$ with increment $<${\bf point{\tt\_}incr}$>$ and the
blocks according to a loop from $<${\bf start{\tt\_}block}$>$ to $<${\bf end{\tt\_}block}$>$ with
increment $<${\bf block{\tt\_}incr}$>$.

The first datum in each block is numbered '0', as is the first block in the
file.

Note that records containing unplottable information are counted.

Any of the numbers can be omitted; the increments default to unity, the start
values to the first point or block, and the end values to the last point or
block.  If {\bf every} is not specified, all points in all lines are plotted.

Examples:
\preverbatim
\begin{verbatim}
     every :::3::3    # selects just the fourth block ('0' is first)
     every :::::9     # selects the first 10 blocks
     every 2:2        # selects every other point in every other block
     every ::5::15    # selects points 5 through 15 in each block
\end{verbatim}
\postverbatim
\subsubsection{Example datafile}
This example plots the data in the file {\tt"}population.dat{\tt"} and a theoretical
curve:

\preverbatim
\begin{verbatim}
     pop(x) = 103*exp((1965-x)/10)
     plot [1960:1990] 'population.dat', pop(x)
\end{verbatim}
\postverbatim

The file {\tt"}population.dat{\tt"} might contain:

\preverbatim
\begin{verbatim}
     # Gnu population in Antarctica since 1965
        1965   103
        1970   55
        1975   34
        1980   24
        1985   10
\end{verbatim}
\postverbatim

\subsubsection{Index}
The {\bf index} keyword allows only some of the data sets in a multi-data-set
file to be plotted.

Syntax:
\preverbatim
\begin{verbatim}
     plot 'file' index <m>{{:<n>}:<p>}
\end{verbatim}
\postverbatim

Data sets are separated by pairs of blank records.  {\bf index $<$m$>$} selects only
set $<$m$>$; {\bf index $<$m$>$:$<$n$>$} selects sets in the range $<$m$>$ to $<$n$>$; and {\bf index
$<$m$>$:$<$n$>$:$<$p$>$} selects indices $<$m$>$, $<$m$>$+$<$p$>$, $<$m$>$+2$<$p$>$, etc., but stopping at
$<$n$>$.  Following C indexing, the index 0 is assigned to the first data set in
the file.  Specifying too large an index results in an error message.  If
{\bf index} is not specified, all sets are plotted as a single data set.

Example:
\preverbatim
\begin{verbatim}
     plot 'file' index 4:5
\end{verbatim}
\postverbatim
\subsubsection{Smooth}
{\bf gnuplot} includes a few general-purpose routines for interpolation and
approximation of data; these are grouped under the {\bf smooth} option.  More
sophisticated data processing may be performed by preprocessing the data
externally or by using {\bf fit} with an appropriate model.

Syntax:
\preverbatim
\begin{verbatim}
     smooth {unique | csplines | acsplines | bezier | sbezier}
\end{verbatim}
\postverbatim

{\bf unique} plots the data after making them monotonic.  Each of the other
routines uses the data to determine the coefficients of a continuous curve
between the endpoints of the data.  This curve is then plotted in the same
manner as a function, that is, by finding its value at uniform intervals
along the abscissa (see {\bf set samples}) and connecting these points with
straight line segments (if a line style is chosen).

If {\bf autoscale} is in effect, the ranges will be computed such that the
plotted curve lies within the borders of the graph.

If too few points are available to allow the selected option to be applied,
an error message is produced.  The minimum number is one for {\bf unique}, four
for {\bf acsplines}, and three for the others.

The {\bf smooth} options have no effect on function plots.
\subsubsubsection{Acsplines}
The {\bf acsplines} option approximates the data with a {\tt"}natural smoothing spline{\tt"}.
After the data are made monotonic in x (see {\bf smooth unique}), a curve is
piecewise constructed from segments of cubic polynomials whose coefficients
are found by the weighting the data points; the weights are taken from the
third column in the data file.  That default can be modified by the third
entry in the {\bf using} list, e.g.,
\preverbatim
\begin{verbatim}
     plot 'data-file' using 1:2:(1.0) smooth acsplines
\end{verbatim}
\postverbatim

Qualitatively, the absolute magnitude of the weights determines the number
of segments used to construct the curve.  If the weights are large, the
effect of each datum is large and the curve approaches that produced by
connecting consecutive points with natural cubic splines.  If the weights are
small, the curve is composed of fewer segments and thus is smoother; the
limiting case is the single segment produced by a weighted linear least
squares fit to all the data.  The smoothing weight can be expressed in terms
of errors as a statistical weight for a point divided by a {\tt"}smoothing factor{\tt"}
for the curve so that (standard) errors in the file can be used as smoothing
weights.

Example:
\preverbatim
\begin{verbatim}
     sw(x,S)=1/(x*x*S)
     plot 'data_file' using 1:2:(sw($3,100)) smooth acsplines
\end{verbatim}
\postverbatim
\subsubsubsection{Bezier}
The {\bf bezier} option approximates the data with a Bezier curve of degree n
(the number of data points) that connects the endpoints.
\subsubsubsection{Csplines}
The {\bf csplines} option connects consecutive points by natural cubic splines
after rendering the data monotonic (see {\bf smooth unique}).
\subsubsubsection{Sbezier}
The {\bf sbezier} option first renders the data monotonic ({\bf unique}) and then
applies the {\bf bezier} algorithm.
\subsubsubsection{Unique}
The {\bf unique} option makes the data monotonic in x; points with the same
x-value are replaced by a single point having the average y-value.  The
resulting points are then connected by straight line segments.
\subsubsection{Special-filenames}
A special filename of {\bf '-'} specifies that the data are inline; i.e., they
follow the command.  Only the data follow the command; {\bf plot} options like
filters, titles, and line styles remain on the 'plot' command line.  This is
similar to $<$$<$ in unix shell script, and \$DECK in VMS DCL.  The data are
entered as though they are being read from a file, one data point per record.
The letter {\tt"}e{\tt"} at the start of the first column terminates data entry.  The
{\bf using} option can be applied to these data --- using it to filter them through
a function might make sense, but selecting columns probably doesn't!

{\bf '-'} is intended for situations where it is useful to have data and commands
together, e.g., when {\bf gnuplot} is run as a sub-process of some front-end
application.  Some of the demos, for example, might use this feature.  While
{\bf plot} options such as {\bf index} and {\bf every} are recognized, their use forces
you to enter data that won't be used.  For example, while

\preverbatim
\begin{verbatim}
     plot '-' index 0, '-' index 1
     2
     4
     6
\end{verbatim}
\postverbatim


\preverbatim
\begin{verbatim}
     10
     12
     14
     e
     2
     4
     6
\end{verbatim}
\postverbatim


\preverbatim
\begin{verbatim}
     10
     12
     14
     e
\end{verbatim}
\postverbatim

does indeed work,

\preverbatim
\begin{verbatim}
     plot '-', '-'
     2
     4
     6
     e
     10
     12
     14
     e
\end{verbatim}
\postverbatim

is a lot easier to type.

If you use {\bf '-'} with {\bf replot}, you may need to enter the data more than once
(see {\bf replot}).

A blank filename ({'\,'}) specifies that the previous filename should be reused.
This can be useful with things like

\preverbatim
\begin{verbatim}
     plot 'a/very/long/filename' using 1:2, '' using 1:3, '' using 1:4
\end{verbatim}
\postverbatim

(If you use both {\bf '-'} and {\bf {'\,'}} on the same {\bf plot} command, you'll need to
have two sets of inline data, as in the example above.)

On some computer systems with a popen function (Unix), the datafile can be
piped through a shell command by starting the file name with a '$<$'.  For
example,

\preverbatim
\begin{verbatim}
     pop(x) = 103*exp(-x/10)
     plot "< awk '{print $1-1965, $2}' population.dat", pop(x)
\end{verbatim}
\postverbatim

would plot the same information as the first population example but with
years since 1965 as the x axis.  If you want to execute this example, you
have to delete all comments from the data file above or substitute the
following command for the first part of the command above (the part up to
the comma):

\preverbatim
\begin{verbatim}
     plot "< awk '$0 !~ /^#/ {print $1-1965, $2}' population.dat"
\end{verbatim}
\postverbatim

While this approach is most flexible, it is possible to achieve simple
filtering with the {\bf using} or {\bf thru} keywords.
\subsubsection{Thru}
The {\bf thru} function is provided for backward compatibility.

Syntax:
\preverbatim
\begin{verbatim}
     plot 'file' thru f(x)
\end{verbatim}
\postverbatim

It is equivalent to:

\preverbatim
\begin{verbatim}
     plot 'file' using 1:(f($2))
\end{verbatim}
\postverbatim

While the latter appears more complex, it is much more flexible.  The more
natural

\preverbatim
\begin{verbatim}
     plot 'file' thru f(y)
\end{verbatim}
\postverbatim

also works (i.e. you can use y as the dummy variable).

{\bf thru} is parsed for {\bf splot} and {\bf fit} but has no effect.
\subsubsection{Using}
The most common datafile modifier is {\bf using}.

Syntax:
\preverbatim
\begin{verbatim}
     plot 'file' using {<entry> {:<entry> {:<entry> ...}}} {'format'}
\end{verbatim}
\postverbatim

If a format is specified, each datafile record is read using the C library's
'scanf' function, with the specified format string.  Otherwise the record is
read and broken into columns at spaces or tabs.  A format cannot be specified
if time-format data is being used (this must be done by {\bf set data time}).

The resulting array of data is then sorted into columns according to the
entries.  Each $<$entry$>$ may be a simple column number, which selects the
datum, an expression enclosed in parentheses, or empty.  The expression can
use \$1 to access the first item read, \$2 for the second item, and so on.  It
can also use {\bf column(x)} and {\bf valid(x)} where x is an arbitrary expression
resulting in an integer.  {\bf column(x)} returns the x'th datum; {\bf valid(x)}
tests that the datum in the x'th column is a valid number.  A column number
of 0 generates a number increasing (from zero) with each point, and is reset
upon encountering two blank records.  A column number of -1 gives the
dataline number, which starts at 0, increments at single blank records, and
is reset at double blank records.  A column number of -2 gives the index
number, which is incremented only when two blank records are found.  An empty
$<$entry$>$ will default to its order in the list of entries.  For example,
{\bf using ::4} is interpreted as {\bf using 1:2:4}.

N.B. --- the {\bf call} command also uses \$'s as a special character.  See {\bf call}
for details about how to include a column number in a {\bf call} argument list.

If the {\bf using} list has but a single entry, that $<$entry$>$ will be used for y
and the data point number is used for x; for example, {\tt"}{\bf plot 'file' using 1}{\tt"}
is identical to {\tt"}{\bf plot 'file' using 0:1}{\tt"}.  If the {\bf using} list has two
entries, these will be used for x and y.  Additional entries are usually
errors in x and/or y.  See {\bf set style} for details about plotting styles that
make use of error information, and {\bf fit} for use of error information in
curve fitting.

'scanf' accepts several numerical specifications but {\bf gnuplot} requires all
inputs to be double-precision floating-point variables, so {\bf lf} is the only
permissible specifier.  'scanf' expects to see white space --- a blank, tab
({\tt"}$\backslash$t{\tt"}), newline ({\tt"}$\backslash$n{\tt"}), or formfeed ({\tt"}$\backslash$f{\tt"}) --- between numbers; anything else
in the input stream must be explicitly skipped.

Note that the use of {\tt"}$\backslash$t{\tt"}, {\tt"}$\backslash$n{\tt"}, or {\tt"}$\backslash$f{\tt"} or requires use of double-quotes
rather than single-quotes.

Examples:

This creates a plot of the sum of the 2nd and 3rd data against the first:
(The format string specifies comma- rather than space-separated columns.)
\preverbatim
\begin{verbatim}
     plot 'file' using 1:($2+$3) '%lf,%lf,%lf'
\end{verbatim}
\postverbatim

In this example the data are read from the file {\tt"}MyData{\tt"} using a more
complicated format:
\preverbatim
\begin{verbatim}
     plot 'MyData' using "%*lf%lf%*20[^\n]%lf"
\end{verbatim}
\postverbatim

The meaning of this format is:

\preverbatim
\begin{verbatim}
     %*lf        ignore a number
     %lf         read a double-precision number (x by default)
     %*20[^\n]   ignore 20 non-newline characters
     %lf         read a double-precision number (y by default)
\end{verbatim}
\postverbatim

One trick is to use the ternary {\bf ?:} operator to filter data:

\preverbatim
\begin{verbatim}
     plot 'file' using 1:($3>10 ? $2 : 1/0)
\end{verbatim}
\postverbatim

which plots the datum in column two against that in column one provided
the datum in column three exceeds ten.  {\bf 1/0} is undefined; {\bf gnuplot}
quietly ignores undefined points, so unsuitable points are suppressed.

In fact, you can use a constant expression for the column number, provided it
doesn't start with an opening parenthesis; constructs like {\bf using
0+(complicated expression)} can be used.  The crucial point is that the
expression is evaluated once if it doesn't start with a left parenthesis, or
once for each data point read if it does.

If timeseries data are being used, the time can span multiple columns.  The
starting column should be specified.  Note that the spaces within the time
must be included when calculating starting columns for other data.  E.g., if
the first element on a line is a time with an embedded space, the y value
should be specified as column three.

It should be noted that {\bf plot 'file'}, {\bf plot 'file' using 1:2}, and {\bf plot
'file' using (\$1):(\$2)} can be subtly different: 1) if {\bf file} has some lines
with one column and some with two, the first will invent x values when they
are missing, the second will quietly ignore the lines with one column, and
the third will store an undefined value for lines with one point (so that in
a plot with lines, no line joins points across the bad point); 2) if a line
contains text at the first column, the first will abort the plot on an error,
but the second and third should quietly skip the garbage.

In fact, it is often possible to plot a file with lots of lines of garbage at
the top simply by specifying

\preverbatim
\begin{verbatim}
     plot 'file' using 1:2
\end{verbatim}
\postverbatim

However, if you want to leave text in your data files, it is safer to put the
comment character (\#) in the first column of the text lines.
\subsection{Errorbars}
Error bars are supported for 2-d data file plots by reading one to four
additional columns (or {\bf using} entries); these additional values are used in
different ways by the various errorbar styles.

In the default situation, {\bf gnuplot} expects to see three, four, or six
numbers on each line of the data file --- either

\preverbatim
\begin{verbatim}
     (x, y, ydelta),
     (x, y, ylow, yhigh),
     (x, y, xdelta),
     (x, y, xlow, xhigh),
     (x, y, xdelta, ydelta), or
     (x, y, xlow, xhigh, ylow, yhigh).
\end{verbatim}
\postverbatim

The x coordinate must be specified.  The order of the numbers must be
exactly as given above, though the {\bf using} qualifier can manipulate the order
and provide values for missing columns.  For example,

\preverbatim
\begin{verbatim}
     plot 'file' with errorbars
     plot 'file' using 1:2:(sqrt($1)) with xerrorbars
     plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars
\end{verbatim}
\postverbatim

The last example is for a file containing an unsupported combination of
relative x and absolute y errors.  The {\bf using} entry generates absolute x min
and max from the relative error.

The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh).
If ydelta is specified instead of ylow and yhigh, ylow = y - ydelta and
yhigh = y + ydelta are derived.  If there are only two numbers on the record,
yhigh and ylow are both set to y.  The x error bar is a horizontal line
computed in the same fashion.  To get lines plotted between the data points,
{\bf plot} the data file twice, once with errorbars and once with lines (but
remember to use the {\bf notitle} option on one to avoid two entries in the key).

The error bars have crossbars at each end unless {\bf set bar} is used (see {\bf set
bar} for details).

If autoscaling is on, the ranges will be adjusted to include the error bars.

See {\bf plot using}, {\bf plot with}, and {\bf set style} for more information.
\subsection{Parametric}
When in parametric mode ({\bf set parametric}) mathematical expressions must be
given in pairs for {\bf plot} and in triplets for {\bf splot}.

Examples:
\preverbatim
\begin{verbatim}
     plot sin(t),t**2
     splot cos(u)*cos(v),cos(u)*sin(v),sin(u)
\end{verbatim}
\postverbatim

Data files are plotted as before, except any preceding parametric function
must be fully specified before a data file is given as a plot.  In other
words, the x parametric function ({\bf sin(t)} above) and the y parametric
function ({\bf t**2} above) must not be interrupted with any modifiers or data
functions; doing so will generate a syntax error stating that the parametric
function is not fully specified.

Other modifiers, such as {\bf with} and {\bf title}, may be specified only after the
parametric function has been completed:

\preverbatim
\begin{verbatim}
     plot sin(t),t**2 title 'Parametric example' with linespoints
\end{verbatim}
\postverbatim
\subsection{Ranges}
The optional ranges specify the region of the graph that will be displayed.

Syntax:
\preverbatim
\begin{verbatim}
     [{<dummy-var>=}{{<min>}:{<max>}}]
     [{{<min>}:{<max>}}]
\end{verbatim}
\postverbatim

The first form applies to the independent variable ({\bf xrange} or {\bf trange}, if
in parametric mode).  The second form applies to the dependent variable
{\bf yrange} (and {\bf xrange}, too, if in parametric mode).  $<$dummy-var$>$ is a new
name for the independent variable.  (The defaults may be changed with {\bf set
dummy}.)  The optional $<$min$>$ and $<$max$>$ terms can be constant expressions or *.

In non-parametric mode, the order in which ranges must be given is {\bf xrange}
and {\bf yrange}.

In parametric mode, the order for the {\bf plot} command is {\bf trange}, {\bf xrange},
and {\bf yrange}.  The following {\bf plot} command shows setting the {\bf trange} to
[-pi:pi], the {\bf xrange} to [-1.3:1.3] and the {\bf yrange} to [-1:1] for the
duration of the graph:

\preverbatim
\begin{verbatim}
     plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2
\end{verbatim}
\postverbatim

Note that the x2range and y2range cannot be specified here --- {\bf set x2range}
and {\bf set y2range} must be used.

Ranges are interpreted in the order listed above for the appropriate mode.
Once all those needed are specified, no further ones must be listed, but
unneeded ones cannot be skipped --- use an empty range {\bf []} as a placeholder.

{\bf *} can be used to allow autoscaling of either of min and max.  See also
{\bf set autoscale}.

Ranges specified on the {\bf plot} or {\bf splot} command line affect only that
graph; use the {\bf set xrange}, {\bf set yrange}, etc., commands to change the
default ranges for future graphs.

With time data, you must provide the range (in the same manner as the time
appears in the datafile) within quotes.  {\bf gnuplot} uses the {\bf timefmt} string
to read the value --- see {\bf set timefmt}.

Examples:

This uses the current ranges:
\preverbatim
\begin{verbatim}
     plot cos(x)
\end{verbatim}
\postverbatim

This sets the x range only:
\preverbatim
\begin{verbatim}
     plot [-10:30] sin(pi*x)/(pi*x)
\end{verbatim}
\postverbatim

This is the same, but uses t as the dummy-variable:
\preverbatim
\begin{verbatim}
     plot [t = -10 :30]  sin(pi*t)/(pi*t)
\end{verbatim}
\postverbatim

This sets both the x and y ranges:
\preverbatim
\begin{verbatim}
     plot [-pi:pi] [-3:3]  tan(x), 1/x
\end{verbatim}
\postverbatim

This sets only the y range, and turns off autoscaling on both axes:
\preverbatim
\begin{verbatim}
     plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)
\end{verbatim}
\postverbatim

This sets xmax and ymin only:
\preverbatim
\begin{verbatim}
     plot [:200] [-pi:]  exp(sin(x))
\end{verbatim}
\postverbatim

This sets the x range for a timeseries:
\preverbatim
\begin{verbatim}
     set timefmt "%d/%m/%y %H:%M"
     plot ["1/6/93 12:00":"5/6/93 12:00"] 'timedata.dat'
\end{verbatim}
\postverbatim

\subsection{Title}
A line title for each function and data set appears in the key, accompanied
by a sample of the line and/or symbol used to represent it.  It can be
changed by using the {\bf title} option.

Syntax:
\preverbatim
\begin{verbatim}
     title "<title>" | notitle
\end{verbatim}
\postverbatim

where $<$title$>$ is the new title of the line and must be enclosed in quotes.
The quotes will not be shown in the key.  A special character may be given as
a backslash followed by its octal value ({\tt"}$\backslash$345{\tt"}).  The tab character {\tt"}$\backslash$t{\tt"} is
understood.  Note that backslash processing occurs only for strings enclosed
in double quotes --- use single quotes to prevent such processing.  The newline
character {\tt"}$\backslash$n{\tt"} is not processed in key entries in either type of string.

The line title and sample can be omitted from the key by using the keyword
{\bf notitle}.  A null title ({\bf title {'\,'}}) is equivalent to {\bf notitle}.  If only
the sample is wanted, use one or more blanks ({\bf title ' '}).

By default the line title is the function or file name as it appears on the
{\bf plot} command.  If it is a file name, any datafile modifiers specified will
be included in the default title.

The layout of the key itself (position, title justification, etc.) can be
controlled by {\bf set key}.  Please see {\bf set key} for details.

Examples:

This plots y=x with the title 'x':
\preverbatim
\begin{verbatim}
     plot x
\end{verbatim}
\postverbatim

This plots x squared with title {\tt"}x\verb+^+2{\tt"} and file {\tt"}data.1{\tt"} with title
{\tt"}measured data{\tt"}:
\preverbatim
\begin{verbatim}
     plot x**2 title "x^2", 'data.1' t "measured data"
\end{verbatim}
\postverbatim

This puts an untitled circular border around a polar graph:
\preverbatim
\begin{verbatim}
     set polar; plot my_function(t), 1 notitle
\end{verbatim}
\postverbatim
\subsection{With}
Functions and data may be displayed in one of a large number of styles.
The {\bf with} keyword provides the means of selection.

Syntax:
\preverbatim
\begin{verbatim}
     with <style> { {linestyle | ls <line_style>}
                    | {{linetype | lt <line_type>}
                       {linewidth | lw <line_width>}
                       {pointtype | pt <point_type>}
                       {pointsize | ps <point_size>}} }
\end{verbatim}
\postverbatim

where $<$style$>$ is either {\bf lines}, {\bf points}, {\bf linespoints}, {\bf impulses}, {\bf dots},
{\bf steps}, {\bf fsteps}, {\bf histeps}, {\bf errorbars}, {\bf xerrorbars}, {\bf yerrorbars},
{\bf xyerrorbars}, {\bf boxes}, {\bf boxerrorbars}, {\bf boxxyerrorbars}, {\bf financebars},
{\bf candlesticks} or {\bf vector}.  Some of these styles require additional
information.  See {\bf set style $<$style$>$} for details of each style.

Default styles are chosen with the {\bf set function style} and {\bf set data style}
commands.

By default, each function and data file will use a different line type and
point type, up to the maximum number of available types.  All terminal
drivers support at least six different point types, and re-use them, in
order, if more are required.  The LaTeX driver supplies an additional six
point types (all variants of a circle), and thus will only repeat after 12
curves are plotted with points.  The PostScript drivers ({\bf postscript})
supplies a total of 64.

If you wish to choose the line or point type for a single plot, $<$line{\tt\_}type$>$
and $<$point{\tt\_}type$>$ may be specified.  These are positive integer constants (or
expressions) that specify the line type and point type to be used for the
plot.  Use {\bf test} to display the types available for your terminal.

You may also scale the line width and point size for a plot by using
$<$line{\tt\_}width$>$ and $<$point{\tt\_}size$>$, which are specified relative to the default
values for each terminal.  The pointsize may also be altered globally --- see
{\bf set pointsize} for details.  But note that both $<$point{\tt\_}size$>$ as set here and
as set by {\bf set pointsize} multiply the default point size --- their effects are
not cumulative.  That is, {\bf set pointsize 2; plot x w p ps 3} will use points
three times default size, not six.

If you have defined specific line type/width and point type/size combinations
with {\bf set linestyle}, one of these may be selected by setting $<$line{\tt\_}style$>$ to
the index of the desired style.

The keywords may be abbreviated as indicated.

Note that the {\bf linewidth} and {\bf pointsize} options are not supported by all
terminals.

Examples:

This plots sin(x) with impulses:
\preverbatim
\begin{verbatim}
     plot sin(x) with impulses
\end{verbatim}
\postverbatim

This plots x with points, x**2 with the default:
\preverbatim
\begin{verbatim}
     plot x*y w points, x**2 + y**2
\end{verbatim}
\postverbatim

This plots tan(x) with the default function style, file {\tt"}data.1{\tt"} with lines:
\preverbatim
\begin{verbatim}
     plot [ ] [-2:5] tan(x), 'data.1' with l
\end{verbatim}
\postverbatim

This plots {\tt"}leastsq.dat{\tt"} with impulses:
\preverbatim
\begin{verbatim}
     plot 'leastsq.dat' w i
\end{verbatim}
\postverbatim

This plots the data file {\tt"}population{\tt"} with boxes:
\preverbatim
\begin{verbatim}
     plot 'population' with boxes
\end{verbatim}
\postverbatim

This plots {\tt"}exper.dat{\tt"} with errorbars and lines connecting the points
(errorbars require three or four columns):
\preverbatim
\begin{verbatim}
     plot 'exper.dat' w lines, 'exper.dat' notitle w errorbars
\end{verbatim}
\postverbatim

This plots sin(x) and cos(x) with linespoints, using the same line type but
different point types:
\preverbatim
\begin{verbatim}
     plot sin(x) with linesp lt 1 pt 3, cos(x) with linesp lt 1 pt 4
\end{verbatim}
\postverbatim

This plots file {\tt"}data{\tt"} with points of type 3 and twice usual size:
\preverbatim
\begin{verbatim}
     plot 'data' with points pointtype 3 pointsize 2
\end{verbatim}
\postverbatim

This plots two data sets with lines differing only by weight:
\preverbatim
\begin{verbatim}
     plot 'd1' t "good" w l lt 2 lw 3, 'd2' t "bad" w l lt 2 lw 1
\end{verbatim}
\postverbatim

See {\bf set style} to change the default styles.
\section{Print}
The {\bf print} command prints the value of $<$expression$>$ to the screen.  It is
synonymous with {\bf pause 0}.  $<$expression$>$ may be anything that {\bf gnuplot} can
evaluate that produces a number, or it can be a string.

Syntax:
\preverbatim
\begin{verbatim}
     print <expression> {, <expression>, ...}
\end{verbatim}
\postverbatim

See {\bf expressions}.
\section{Pwd}
The {\bf pwd} command prints the name of the working directory to the screen.
\section{Quit}
The {\bf exit} and {\bf quit} commands and END-OF-FILE character will exit {\bf gnuplot}.
Each of these commands will clear the output device (as does the {\bf clear}
command) before exiting.
\section{Replot}
The {\bf replot} command without arguments repeats the last {\bf plot} or {\bf splot}
command.  This can be useful for viewing a plot with different {\bf set} options,
or when generating the same plot for several devices.

Arguments specified after a {\bf replot} command will be added onto the last
{\bf plot} or {\bf splot} command (with an implied ',' separator) before it is
repeated.  {\bf replot} accepts the same arguments as the {\bf plot} and {\bf splot}
commands except that ranges cannot be specified.  Thus you can use {\bf replot}
to plot a function against the second axes if the previous command was {\bf plot}
but not if it was {\bf splot}, and similarly you can use {\bf replot} to add a plot
from a binary file only if the previous command was {\bf splot}.

N.B. --- use of

\preverbatim
\begin{verbatim}
     plot '-' ; ... ; replot
\end{verbatim}
\postverbatim

is not recommended.  {\bf gnuplot} does not store the inline data internally, so
since {\bf replot} appends new information to the previous {\bf plot} and then
executes the modified command, the {\bf '-'} from the initial {\bf plot} will expect
to read inline data again.

Note that {\bf replot} does not work in {\bf multiplot} mode, since it reproduces
only the last plot rather than the entire screen.

See also {\bf command-line-editing} for ways to edit the last {\bf plot} ({\bf splot})
command.
\section{Reread}
The {\bf reread} command causes the current {\bf gnuplot} command file, as specified
by a {\bf load} command or on the command line, to be reset to its starting
point before further commands are read from it.  This essentially implements
an endless loop of the commands from the beginning of the command file to
the {\bf reread} command.  (But this is not necessarily a disaster --- {\bf reread} can
be very useful when used in conjunction with {\bf if}.  See {\bf if} for details.)
The {\bf reread} command has no effect if input from standard input.

Examples:

Suppose the file {\tt"}looper{\tt"} contains the commands
\preverbatim
\begin{verbatim}
     a=a+1
     plot sin(x*a)
     pause -1
     if(a<5) reread
\end{verbatim}
\postverbatim
and from within {\bf gnuplot} you submit the commands
\preverbatim
\begin{verbatim}
     a=0
     load 'looper'
\end{verbatim}
\postverbatim
The result will be four plots (separated by the {\bf pause} message).

Suppose the file {\tt"}data{\tt"} contains six columns of numbers with a total yrange
from 0 to 10; the first is x and the next are five different functions of x.
Suppose also that the file {\tt"}plotter{\tt"} contains the commands
\preverbatim
\begin{verbatim}
     c_p = c_p+1
     plot "$0" using 1:c_p with lines linetype c_p
     if(c_p <  n_p) reread
\end{verbatim}
\postverbatim
and from within {\bf gnuplot} you submit the commands
\preverbatim
\begin{verbatim}
     n_p=6
     c_p=1
     set nokey
     set yrange [0:10]
     set multiplot
     call 'plotter' 'data'
     set nomultiplot
\end{verbatim}
\postverbatim
The result is a single graph consisting of five plots.  The yrange must be
set explicitly to guarantee that the five separate graphs (drawn on top of
each other in multiplot mode) will have exactly the same axes.  The linetype
must be specified; otherwise all the plots would be drawn with the same type.
\section{Reset}
The {\bf reset} command causes all options that can be set with the {\bf set}
command to take on their default values.  The only exceptions are that the
terminal set with {\bf set term} and the output file set with {\bf set output} are
left unchanged.  This command is useful, e.g., to restore the default
settings at the end of a command file, or to return to a defined state after
lots of settings have been changed within a command file.  Please refer to
the {\bf set} command to see the default values that the various options take.
\section{Save}
The {\bf save} command saves user-defined functions, variables, {\bf set} options,
or all three, plus the last {\bf plot} ({\bf splot}) command to the specified file.

Syntax:
\preverbatim
\begin{verbatim}
     save  {<option>} '<filename>'
\end{verbatim}
\postverbatim

where $<$option$>$ is {\bf functions}, {\bf variables} or {\bf set}. If no option is used,
{\bf gnuplot} saves functions, variables, {\bf set} options and the last {\bf plot}
({\bf splot}) command.

{\bf save}d files are written in text format and may be read by the {\bf load}
command.

The filename must be enclosed in quotes.

Examples:
\preverbatim
\begin{verbatim}
     save 'work.gnu'
     save functions 'func.dat'
     save var 'var.dat'
     save set 'options.dat'
\end{verbatim}
\postverbatim
\section{Set-show}
The {\bf set} command can be used to sets {\em lots\/} of options.  No screen is
drawn, however, until a {\bf plot}, {\bf splot}, or {\bf replot} command is given.

The {\bf show} command shows their settings;  {\bf show all} shows all the
settings.

If a variable contains time/date data, {\bf show} will display it according to
the format currently defined by {\bf set timefmt}, even if that was not in effect
when the variable was initially defined.
\subsection{Angles}
By default, {\bf gnuplot} assumes the independent variable in polar graphs is in
units of radians.  If {\bf set angles degrees} is specified before {\bf set polar},
then the default range is [0:360] and the independent variable has units of
degrees.  This is particularly useful for plots of data files.  The angle
setting also applies to 3-d mapping as set via the {\bf set mapping} command.

Syntax:
\preverbatim
\begin{verbatim}
     set angles {degrees | radians}
     show angles
\end{verbatim}
\postverbatim

The angle specified in {\bf set grid polar} is also read and displayed in the
units specified by {\bf set angles}.

{\bf set angles} also affects the arguments of the machine-defined functions
sin(x), cos(x) and tan(x), and the outputs of asin(x), acos(x), atan(x),
atan2(x), and arg(x).  It has no effect on the arguments of hyperbolic
functions or Bessel functions.  However, the output arguments of inverse
hyperbolic functions of complex arguments are affected; if these functions
are used, {\bf set angles radians} must be in effect to maintain consistency
between input and output arguments.

\preverbatim
\begin{verbatim}
     x={1.0,0.1}
     set angles radians
     y=sinh(x)
     print y         #prints {1.16933, 0.154051}
     print asinh(y)  #prints {1.0, 0.1}
\end{verbatim}
\postverbatim
but
\preverbatim
\begin{verbatim}
     set angles degrees
     y=sinh(x)
     print y         #prints {1.16933, 0.154051}
     print asinh(y)  #prints {57.29578, 5.729578}
\end{verbatim}
\postverbatim
\subsection{Arrow}
Arbitrary arrows can be placed on a plot using the {\bf set arrow} command.

Syntax:
\preverbatim
\begin{verbatim}
     set arrow {<tag>} {from <position>} {to <position>} {{no}head}
               { {linestyle | ls <line_style>}
                 | {linetype | lt <line_type>}
                   {linewidth | lw <line_width} }
     set noarrow {<tag>}
     show arrow
\end{verbatim}
\postverbatim

$<$tag$>$ is an integer that identifies the arrow.  If no tag is given, the
lowest unused tag value is assigned automatically.  The tag can be used to
delete or change a specific arrow.  To change any attribute of an existing
arrow, use the {\bf set arrow} command with the appropriate tag and specify the
parts of the arrow to be changed.

The $<$position$>$s are specified by either x,y or x,y,z, and may be preceded by
{\bf first}, {\bf second}, {\bf graph}, or {\bf screen} to select the coordinate system.
Unspecified coordinates default to 0.  The endpoints can be specified in
one of four coordinate systems --- {\bf first} or {\bf second} axes, {\bf graph} or
{\bf screen}.  See {\bf coordinates} for details.  A coordinate system specifier
does not carry over from the {\tt"}from{\tt"} position to the {\tt"}to{\tt"} position.  Arrows
outside the screen boundaries are permitted but may cause device errors.

Specifying {\bf nohead} produces an arrow drawn without a head --- a line segment.
This gives you yet another way to draw a line segment on the plot.  By
default, arrows have heads.

The line style may be selected from a user-defined list of line styles (see
{\bf set linestyle}) or may be defined here by providing values for $<$line{\tt\_}type$>$
(an index from the default list of styles) and/or $<$line{\tt\_}width$>$ (which is a
multiplier for the default width).

Note, however, that if a user-defined line style has been selected, its
properties (type and width) cannot be altered merely by issuing another
{\bf set arrow} command with the appropriate index and {\bf lt} or {\bf lw}.

Examples:

To set an arrow pointing from the origin to (1,2) with user-defined style 5,
use:
\preverbatim
\begin{verbatim}
     set arrow to 1,2 ls 5
\end{verbatim}
\postverbatim

To set an arrow from bottom left of plotting area to (-5,5,3), and tag the
arrow number 3, use:
\preverbatim
\begin{verbatim}
     set arrow 3 from graph 0,0 to -5,5,3
\end{verbatim}
\postverbatim

To change the preceding arrow to end at 1,1,1, without an arrow head and
double its width, use:
\preverbatim
\begin{verbatim}
     set arrow 3 to 1,1,1 nohead lw 2
\end{verbatim}
\postverbatim

To draw a vertical line from the bottom to the top of the graph at x=3, use:
\preverbatim
\begin{verbatim}
     set arrow from 3, graph 0 to 3, graph 1 nohead
\end{verbatim}
\postverbatim

To delete arrow number 2, use:
\preverbatim
\begin{verbatim}
     set noarrow 2
\end{verbatim}
\postverbatim

To delete all arrows, use:
\preverbatim
\begin{verbatim}
     set noarrow
\end{verbatim}
\postverbatim

To show all arrows (in tag order), use:
\preverbatim
\begin{verbatim}
     show arrow
\end{verbatim}
\postverbatim
\subsection{Autoscale}
Autoscaling may be set individually on the x, y or z axis or globally on all
axes. The default is to autoscale all axes.

Syntax:
\preverbatim
\begin{verbatim}
     set autoscale {<axes>{min|max}}
     set noautoscale {<axes>{min|max}}
     show autoscale
\end{verbatim}
\postverbatim

where $<$axes$>$ is either {\bf x}, {\bf y}, {\bf z}, {\bf x2}, {\bf y2} or {\bf xy}.  A keyword with
{\bf min} or {\bf max} appended (this cannot be done with {\bf xy}) tells {\bf gnuplot} to
autoscale just the minimum or maximum of that axis.  If no keyword is given,
all axes are autoscaled.

When autoscaling, the axis range is automatically computed and the dependent
axis (y for a {\bf plot} and z for {\bf splot}) is scaled to include the range of the
function or data being plotted.

If autoscaling of the dependent axis (y or z) is not set, the current y or z
range is used.

Autoscaling the independent variables (x for {\bf plot} and x,y for {\bf splot}) is a
request to set the domain to match any data file being plotted.  If there are
no data files, autoscaling an independent variable has no effect.  In other
words, in the absence of a data file, functions alone do not affect the x
range (or the y range if plotting z = f(x,y)).

Please see {\bf set xrange} for additional information about ranges.

The behavior of autoscaling remains consistent in parametric mode, (see {\bf set
parametric}).  However, there are more dependent variables and hence more
control over x, y, and z axis scales.  In parametric mode, the independent or
dummy variable is t for {\bf plot}s and u,v for {\bf splot}s.  {\bf autoscale} in
parametric mode, then, controls all ranges (t, u, v, x, y, and z) and allows
x, y, and z to be fully autoscaled.

Autoscaling works the same way for polar mode as it does for parametric mode
for {\bf plot}, with the extension that in polar mode {\bf set dummy} can be used to
change the independent variable from t (see {\bf set dummy}).

When tics are displayed on second axes but no plot has been specified for
those axes, x2range and y2range are inherited from xrange and yrange.  This
is done {\em before\/} xrange and yrange are autoextended to a whole number of
tics, which can cause unexpected results.

Examples:

This sets autoscaling of the y axis (other axes are not affected):
\preverbatim
\begin{verbatim}
     set autoscale y
\end{verbatim}
\postverbatim

This sets autoscaling only for the minimum of the y axis (the maximum of the
y axis and the other axes are not affected):
\preverbatim
\begin{verbatim}
     set autoscale ymin
\end{verbatim}
\postverbatim

This sets autoscaling of the x and y axes:
\preverbatim
\begin{verbatim}
     set autoscale xy
\end{verbatim}
\postverbatim

This sets autoscaling of the x, y, z, x2 and y2 axes:
\preverbatim
\begin{verbatim}
     set autoscale
\end{verbatim}
\postverbatim

This disables autoscaling of the x, y, z, x2 and y2 axes:
\preverbatim
\begin{verbatim}
     set noautoscale
\end{verbatim}
\postverbatim

This disables autoscaling of the z axis only:
\preverbatim
\begin{verbatim}
     set noautoscale z
\end{verbatim}
\postverbatim
\subsubsection{Parametric mode}
When in parametric mode ({\bf set parametric}), the xrange is as fully scalable
as the y range.  In other words, in parametric mode the x axis can be
automatically scaled to fit the range of the parametric function that is
being plotted.  Of course, the y axis can also be automatically scaled just
as in the non-parametric case.  If autoscaling on the x axis is not set, the
current x range is used.

Data files are plotted the same in parametric and non-parametric mode.
However, there is a difference in mixed function and data plots: in
non-parametric mode with autoscaled x, the x range of the datafile controls
the x range of the functions; in parametric mode it has no influence.

For completeness a last command {\bf set autoscale t} is accepted.  However, the
effect of this {\tt"}scaling{\tt"} is very minor.  When {\bf gnuplot} determines that the
t range would be empty, it makes a small adjustment if autoscaling is true.
Otherwise, {\bf gnuplot} gives an error.  Such behavior may, in fact, not be very
useful and the command {\bf set autoscale t} is certainly questionable.

{\bf splot} extends the above ideas as you would expect.  If autoscaling is set,
then x, y, and z ranges are computed and each axis scaled to fit the
resulting data.
\subsubsection{Polar mode}
When in polar mode ({\bf set polar}), the xrange and the yrange are both found
from the polar coordinates, and thus they can both be automatically scaled.
In other words, in polar mode both the x and y axes can be automatically
scaled to fit the ranges of the polar function that is being plotted.

When plotting functions in polar mode, the rrange may be autoscaled.  When
plotting data files in polar mode, the trange may also be autoscaled.  Note
that if the trange is contained within one quadrant, autoscaling will produce
a polar plot of only that single quadrant.

Explicitly setting one or two ranges but not others may lead to unexpected
results.
\subsection{Bar}
The {\bf set bar} command controls the tics at the ends of errorbars.

Syntax:
\preverbatim
\begin{verbatim}
     set bar {small | large | <size>}
     show bar
\end{verbatim}
\postverbatim

{\bf small} is a synonym for 0.0, and {\bf large} for 1.0.
The default is 1.0 if no size is given.
\subsection{Bmargin}
The command {\bf set bmargin} sets the size of the bottom margin.  Please see
{\bf set margin} for details.
\subsection{Border}
The {\bf set border} and {\bf set noborder} commands control the display of the graph
borders for the {\bf plot} and {\bf splot} commands.

Syntax:
\preverbatim
\begin{verbatim}
     set border {<integer> { {linestyle | ls <line_style>}
                             | {linetype | lt <line_type> }
                               {linewidth | lw <line_width>} } }
     set noborder
     show border
\end{verbatim}
\postverbatim

The borders are encoded in a 12-bit integer: the bottom four bits control the
border for {\bf plot} and the sides of the base for {\bf splot}; The next four bits
control the verticals in {\bf splot}; the top four bits control the edges on top
of the {\bf splot}.  In detail, the {\bf $<$integer$>$} should be the sum of the
appropriate entries from the following table:


\begin{center}
\begin{tabular}{|cc|ccc|} \hline
\multicolumn{5}{|c|}{Graph Border Encoding} \\ \hline \hline
 & & \multicolumn{3}{|c|}{Integer value of selection bit} \\ \cline{3-5}
 & & plot border & splot & splot \\
\multicolumn{2}{|c|}{Side}& splot base & verticals & top \\ \hline
bottom & (south) & 1 & 16 & 256 \\
left   & (west)  & 2 & 32 & 512 \\
top    & (north) & 4 & 64 & 1024 \\
right  & (east)  & 8 & 128 & 2048 \\
\hline
\end{tabular}
\end{center}

The default is 31, which is all four sides for {\bf plot}, and base and z axis
for {\bf splot}.

Using the optional $<$line{\tt\_}style$>$, $<$line{\tt\_}type$>$ and $<$line{\tt\_}width$>$
specifiers, the way the border lines are drawn can be influenced
(limited by what the current terminal driver supports).  By default,
the border is drawn with twice the usual linewidth.  The $<$line{\tt\_}width$>$
specifier scales this default value; for example, {\bf set border 15 lw 2}
will produce a border with four times the usual linewidth.

Various axes or combinations of axes may be added together in the command.

To have tics on edges other than bottom and left, disable the usual tics and
enable the second axes.

Examples:

Draw all borders:
\preverbatim
\begin{verbatim}
     set border
\end{verbatim}
\postverbatim

Draw only the SOUTHWEST borders:
\preverbatim
\begin{verbatim}
     set border 3
\end{verbatim}
\postverbatim

Draw a complete box around a {\bf splot}:
\preverbatim
\begin{verbatim}
     set border 4095
\end{verbatim}
\postverbatim

Draw a partial box, omitting the front vertical:
\preverbatim
\begin{verbatim}
     set border 127+256+512
\end{verbatim}
\postverbatim

Draw only the NORTHEAST borders:
\preverbatim
\begin{verbatim}
     set noxtics; set noytics; set x2tics; set y2tics; set border 12
\end{verbatim}
\postverbatim

\subsection{Boxwidth}
The {\bf set boxwidth} command is used to set the default width of boxes in the
{\bf boxes} and {\bf boxerrorbars} styles.

Syntax:
\preverbatim
\begin{verbatim}
     set boxwidth {<width>}
     show boxwidth
\end{verbatim}
\postverbatim

If a data file is plotted without the width being specified in the third,
fourth, or fifth column (or {\bf using} entry), or if a function is plotted, the
width of each box is set by the {\bf set boxwidth} command.  (If a width is given
both in the file and by the {\bf set boxwidth} command, the one in the file is
used.)  If the width is not specified in one of these ways, the width of each
box will be calculated automatically so that it touches the adjacent boxes.
In a four-column data set, the fourth column will be interpreted as the box
width unless the width is set to -2.0, in which case the width will be
calculated automatically.  See {\bf set style boxerrorbars} for more details.

To set the box width to automatic use the command
\preverbatim
\begin{verbatim}
     set boxwidth
\end{verbatim}
\postverbatim
or, for four-column data,
\preverbatim
\begin{verbatim}
     set boxwidth -2
\end{verbatim}
\postverbatim

The same effect can be achieved with the {\bf using} keyword in {\bf plot}:
\preverbatim
\begin{verbatim}
     plot 'file' using 1:2:3:4:(-2)
\end{verbatim}
\postverbatim
\subsection{Clabel}
{\bf gnuplot} will vary the linetype used for each contour level when clabel is
set.  When this option on (the default), a legend labels each linestyle with
the z level it represents.  It is not possible at present to separate the
contour labels from the surface key.

Syntax:
\preverbatim
\begin{verbatim}
     set clabel {'<format>'}
     set noclabel
     show clabel
\end{verbatim}
\postverbatim

The default for the format string is \%8.3g, which gives three decimal places.
This may produce poor label alignment if the key is altered from its default
configuration.

The first contour linetype, or only contour linetype when clabel is off, is
the surface linetype +1; contour points are the same style as surface points.

See also {\bf set contour}.
\subsection{Clip}
{\bf gnuplot} can clip data points and lines that are near the boundaries of a
graph.

Syntax:
\preverbatim
\begin{verbatim}
     set clip <clip-type>
     set noclip <clip-type>
     show clip
\end{verbatim}
\postverbatim

Three clip types are supported by {\bf gnuplot}: {\bf points}, {\bf one}, and {\bf two}.
One, two, or all three clip types may be active for a single graph.

The {\bf points} clip type forces {\bf gnuplot} to clip (actually, not plot at all)
data points that fall within but too close to the boundaries.  This is done
so that large symbols used for points will not extend outside the boundary
lines.  Without clipping points near the boundaries, the plot may look bad.
Adjusting the x and y ranges may give similar results.

Setting the {\bf one} clip type causes {\bf gnuplot} to draw a line segment which has
only one of its two endpoints within the graph.  Only the in-range portion of
the line is drawn.  The alternative is to not draw any portion of the line
segment.

Some lines may have both endpoints out of range, but pass through the graph.
Setting the {\bf two} clip-type allows the visible portion of these lines to be
drawn.

In no case is a line drawn outside the graph.

The defaults are {\bf noclip points}, {\bf clip one}, and {\bf noclip two}.

To check the state of all forms of clipping, use
\preverbatim
\begin{verbatim}
     show clip
\end{verbatim}
\postverbatim

For backward compatibility with older versions, the following forms are also
permitted:
\preverbatim
\begin{verbatim}
     set clip
     set noclip
\end{verbatim}
\postverbatim

{\bf set clip} is synonymous with {\bf set clip points}; {\bf set noclip} turns off all
three types of clipping.
\subsection{Cntrparam}
{\bf set cntrparam} controls the generation of contours and their smoothness for
a contour plot. {\bf show contour} displays current settings of {\bf cntrparam} as
well as {\bf contour}.

Syntax:
\preverbatim
\begin{verbatim}
     set cntrparam {  {linear | cubicspline | bspline}
                     { points <n>} { order <n> }
                     { levels   auto {<n>} | <n>
                              | discrete <z1> {,<z2>{,<z3>...}}
                              | incremental <start>, <incr> {,<end>}
                      }
                    }
     show contour
\end{verbatim}
\postverbatim

This command has two functions.  First, it sets the values of z for which
contour points are to be determined (by linear interpolation between data
points or function isosamples.)  Second, it controls the way contours are
drawn between the points determined to be of equal z.  $<$n$>$ should be an
integral constant expression and $<$z1$>$, $<$z2$>$ ... any constant expressions.
The parameters are:

{\bf linear}, {\bf cubicspline}, {\bf bspline} --- Controls type of approximation or
interpolation.  If {\bf linear}, then straight line segments connect points of
equal z magnitude.  If {\bf cubicspline}, then piecewise-linear contours are
interpolated between the same equal z points to form somewhat smoother
contours, but which may undulate.  If {\bf bspline}, a guaranteed-smoother curve
is drawn, which only approximates the position of the points of equal-z.

{\bf points} --- Eventually all drawings are done with piecewise-linear strokes.
This number controls the number of line segments used to approximate the
{\bf bspline} or {\bf cubicspline} curve.  Number of cubicspline or bspline
segments (strokes) = {\bf points} * number of linear segments.

{\bf order} --- Order of the bspline approximation to be used.  The bigger this
order is, the smoother the resulting contour.  (Of course, higher order
bspline curves will move further away from the original piecewise linear
data.)  This option is relevant for {\bf bspline} mode only.  Allowed values are
integers in the range from 2 (linear) to 10.

{\bf levels} ---  Selection of contour levels,  controlled by {\bf auto} (default),
{\bf discrete}, {\bf incremental}, and $<$n$>$, number of contour levels, limited to
\preverbatim
\begin{verbatim}
MAX_DISCRETE_LEVELS as defined in plot.h (30 is standard.)
\end{verbatim}
\postverbatim

For {\bf auto}, $<$n$>$ specifies a nominal number of levels; the actual number will
be adjusted to give simple labels. If the surface is bounded by zmin and zmax,
contours will be generated at integer multiples of dz between zmin and zmax,
where dz is 1, 2, or 5 times some power of ten (like the step between two
tic marks).

For {\bf levels discrete}, contours will be generated at z = $<$z1$>$, $<$z2$>$ ... as
specified; the number of discrete levels sets the number of contour levels.
In {\bf discrete} mode, any {\bf set cntrparms levels $<$n$>$} are ignored.

For {\bf incremental}, contours are generated at values of z beginning at $<$start$>$
and increasing by $<$increment$>$, until the number of contours is reached. $<$end$>$
is used to determine the number of contour levels, which will be changed by
any subsequent {\bf set cntrparam levels $<$n$>$}.

If the command {\bf set cntrparam} is given without any arguments specified,  the
defaults are used: linear, 5 points, order 4, 5 auto levels.

Examples:
\preverbatim
\begin{verbatim}
     set cntrparam bspline
     set cntrparam points 7
     set cntrparam order 10
\end{verbatim}
\postverbatim

To select levels automatically, 5 if the level increment criteria are met:
\preverbatim
\begin{verbatim}
     set cntrparam levels auto 5
\end{verbatim}
\postverbatim

To specify discrete levels at .1, .37, and .9:
\preverbatim
\begin{verbatim}
     set cntrparam levels discrete .1,1/exp(1),.9
\end{verbatim}
\postverbatim

To specify levels from 0 to 4 with increment 1:
\preverbatim
\begin{verbatim}
     set cntrparam levels incremental  0,1,4
\end{verbatim}
\postverbatim

To set the number of levels to 10 (changing an incremental end or possibly
the number of auto levels):
\preverbatim
\begin{verbatim}
     set cntrparam levels 10
\end{verbatim}
\postverbatim

To set the start and increment while retaining the number of levels:
\preverbatim
\begin{verbatim}
     set cntrparam levels incremental 100,50
\end{verbatim}
\postverbatim

See also {\bf set contour} for control of where the contours are drawn, and {\bf set
clabel} for control of the format of the contour labels and linetypes.
\subsection{Contour}
{\bf set contour} enables contour drawing for surfaces. This option is available
for {\bf splot} only.

Syntax:
\preverbatim
\begin{verbatim}
     set contour {base | surface | both}
     set nocontour
     show contour
\end{verbatim}
\postverbatim

The three options specify where to draw the contours: {\bf base} draws the
contours on the grid base where the x/ytics are placed, {\bf surface} draws the
contours on the surfaces themselves, and {\bf both} draws the contours on both
the base and the surface.  If no option is provided, the default is {\bf base}.

See also {\bf set cntrparam} for the parameters that affect the drawing of
contours, and {\bf set clabel} for control of labelling of the contours.

The surface can be switched off (see {\bf set surface}), giving a contour-only
graph.  Though it is possible to use {\bf set size} to enlarge the plot to fill
the screen, more control over the output format can be obtained by writing
the contour information to a file, and rereading it as a 2-d datafile plot:

\preverbatim
\begin{verbatim}
     set nosurface
     set contour
     set cntrparam ...
     set term table
     set out 'filename'
     splot ...
     set out
     # contour info now in filename
     set term <whatever>
     plot 'filename'
\end{verbatim}
\postverbatim

In order to draw contours, the data should be organized as {\tt"}grid data{\tt"}.  In
such a file all the points for a single y-isoline are listed, then all the
points for the next y-isoline, and so on.  A single blank line (a line
containing no characters other than blank spaces and a carriage return and/or
a line feed) separates one y-isoline from the next.  See also {\bf splot datafile}.

If contours are desired from non-grid data, {\bf set dgrid3d} can be used to
create an appropriate grid.  See {\bf set dgrid3d} for more information.
\subsection{Data style}
The {\bf set data style} command changes the default plotting style for data
plots.

Syntax:
\preverbatim
\begin{verbatim}
     set data style <style-choice>
     show data style
\end{verbatim}
\postverbatim

See {\bf set style} for the choices.  If no choice is given, the choices are
listed.  {\bf show data style} shows the current default data plotting style.
\subsection{Dgrid3d}
The {\bf set dgrid3d} command enables, and can set parameters for, non-grid
to grid data mapping.

Syntax:
\preverbatim
\begin{verbatim}
     set dgrid3d {<row_size>} {,{<col_size>} {,<norm>}}
     set nodgrid3d
     show dgrid3d
\end{verbatim}
\postverbatim

By default {\bf dgrid3d} is disabled.  When enabled, 3-d data read from a file
are always treated as a scattered data set.  A grid with dimensions derived
from a bounding box of the scattered data and size as specified by the
row/col{\tt\_}size parameters is created for plotting and contouring.  The grid
is equally spaced in x (rows) and in y (columns); the z values are computed
as weighted averages of the scattered points' z values.

The third parameter, norm, controls the weighting:  Each data point is
weighted inversely by its distance from the grid point raised to the norm
power.  (Actually, the weights are given by the inverse of dx\verb+^+norm + dy\verb+^+norm,
where dx and dy are the components of the separation of the grid point from
each data point.  For some norms that are powers of two, specifically 4, 8,
and 16, the computation is optimized by using the Euclidean distance in the
weight calculation, (dx\verb+^+2+dx\verb+^+2)\verb+^+norm/2.  However, any non-negative integer
can be used.)

The closer the data point is to a grid point, the more effect it has on
that grid point and the larger the value of norm the less effect more
distant data points have on that grid point.

The {\bf dgrid3d} option is a simple low pass filter that converts scattered
data to a grid data set.  More sophisticated approaches to this problem
exist and should be used to preprocess the data outside {\bf gnuplot} if this
simple solution is found inadequate.

(The z values are found by weighting all data points, not by interpolating
between nearby data points;  also edge effects may produce unexpected and/or
undesired results.  In some cases, small norm values produce a grid point
reflecting the average of distant data points rather than a local average,
while large values of norm may produce {\tt"}steps{\tt"} with several grid points
having the same value as the closest data point, rather than making a smooth
transition between adjacent data points.  Some areas of a grid may be filled
by extrapolation, to an arbitrary boundary condition.  The variables are
not normalized; consequently the units used for x and y will affect the
relative weights of points in the x and y directions.)

Examples:
\preverbatim
\begin{verbatim}
     set dgrid3d 10,10,1     # defaults
     set dgrid3d ,,4
\end{verbatim}
\postverbatim

The first specifies that a grid of size 10 by 10 is to be constructed using
a norm value of 1 in the weight computation.  The second only modifies the
norm, changing it to 4.

\subsection{Dummy}
The {\bf set dummy} command changes the default dummy variable names.

Syntax:
\preverbatim
\begin{verbatim}
     set dummy {<dummy-var>} {,<dummy-var>}
     show dummy
\end{verbatim}
\postverbatim

By default, {\bf gnuplot} assumes that the independent, or {\tt"}dummy{\tt"}, variable for
the {\bf plot} command is {\tt"}t{\tt"} if in parametric or polar mode, or {\tt"}x{\tt"} otherwise.
Similarly the independent variables for the {\bf splot} command are {\tt"}u{\tt"} and {\tt"}v{\tt"}
in parametric mode ({\bf splot} cannot be used in polar mode), or {\tt"}x{\tt"} and {\tt"}y{\tt"}
otherwise.

It may be more convenient to call a dummy variable by a more physically
meaningful or conventional name.  For example, when plotting time functions:

\preverbatim
\begin{verbatim}
     set dummy t
     plot sin(t), cos(t)
\end{verbatim}
\postverbatim

At least one dummy variable must be set on the command; {\bf set dummy} by itself
will generate an error message.

Examples:
\preverbatim
\begin{verbatim}
     set dummy u,v
     set dummy ,s
\end{verbatim}
\postverbatim

The second example sets the second variable to s.
\subsection{Encoding}
The {\bf set encoding} command selects a character encoding.  Valid values are
{\bf default}, which tells a terminal to use its default; {\bf iso{\tt\_}8859{\tt\_}1} (known in
the PostScript world as {\bf ISO-Latin1}), which is used on many Unix workstations
and with MS-Windows; {\bf cp850}, for OS/2; and {\bf cp437}, for MS-DOS.

Syntax:
\preverbatim
\begin{verbatim}
     set encoding {<value>}
     show encoding
\end{verbatim}
\postverbatim

Note that encoding is not supported by all terminal drivers and that
the device must be able to produce the desired non-standard characters.
\subsection{Format}
The format of the tic-mark labels can be set with the {\bf set format} command.

Syntax:
\preverbatim
\begin{verbatim}
     set format {<axes>} {"<format-string>"}
     set format {<axes>} {'<format-string>'}
     show format
\end{verbatim}
\postverbatim

where $<$axes$>$ is either {\bf x}, {\bf y}, {\bf z}, {\bf xy}, {\bf x2}, {\bf y2} or nothing (which is
the same as {\bf xy}).  The length of the string representing a tic mark (after
formatting with 'printf') is restricted to 100 characters.  If the format
string is omitted, the format will be returned to the default {\tt"}\%g{\tt"}.  For
LaTeX users, the format {\tt"}\$\%g\${\tt"} is often desirable.  If the empty string {\tt"}{\tt"} is
used, no label will be plotted with each tic, though the tic mark will still
be plotted.  To eliminate all tic marks, use {\bf set noxtics} or {\bf set noytics}.

Newline ($\backslash$n) is accepted in the format string.  Use double-quotes rather than
single-quotes to enable such interpretation.  See also {\bf syntax}.

The default format for both axes is {\tt"}\%g{\tt"}, but other formats such as {\tt"}\%.2f{\tt"} or
{\tt"}\%3.0em{\tt"} are often desirable.  Anything accepted by 'printf' when given a
double precision number, and accepted by the terminal, will work.  Some other
options have been added.  If the format string looks like a floating point
format, then {\bf gnuplot} tries to construct a reasonable format.

Characters not preceded by {\tt"}\%{\tt"} are printed verbatim.  Thus you can include
spaces and labels in your format string, such as {\tt"}\%g m{\tt"}, which will put {\tt"} m{\tt"}
after each number.  If you want {\tt"}\%{\tt"} itself, double it: {\tt"}\%g \%\%{\tt"}.

See also {\bf set xtics} for more information about tic labels.
\subsubsection{Format specifiers}
The acceptable formats (if not in time/date mode) are:


\begin{center}
\begin{tabular}{|cl|} \hline
\multicolumn{2}{|c|}{Tic-mark label numerical format specifiers}\\
\hline \hline
Format & Explanation \\ \hline
\verb@%f@ & floating point notation \\
\verb@%e@ or \verb@%E@ & exponential notation; an "e" or "E" before the power \\
\verb@%g@ or \verb@%G@ & the shorter of \verb@%e@ (or \verb@%E@) and \verb@%f@ \\
\verb@%x@ or \verb@%X@ & hex \\
\verb@%o@ or \verb@%O@ & octal \\
\verb@%t@ & mantissa to base 10 \\
\verb@%l@ & mantissa to base of current logscale \\
\verb@%s@ & mantissa to base of current logscale; scientific power \\
\verb@%T@ & power to base 10 \\
\verb@%L@ & power to base of current logscale \\
\verb@%S@ & scientific power \\
\verb@%c@ & character replacement for scientific power \\
\verb@%P@ & multiple of pi \\
\hline
\end{tabular}
\end{center}

A 'scientific' power is one such that the exponent is a multiple of three.
Character replacement of scientific powers ({\bf {\tt"}\%c{\tt"}}) has been implemented
for powers in the range -18 to +18.  For numbers outside of this range the
format reverts to exponential.

Other acceptable modifiers (which come after the {\tt"}\%{\tt"} but before the format
specifier) are {\tt"}-{\tt"}, which left-justifies the number; {\tt"}+{\tt"}, which forces all
numbers to be explicitly signed; {\tt"}\#{\tt"}, which places a decimal point after
floats that have only zeroes following the decimal point; a positive integer,
which defines the field width; {\tt"}0{\tt"} (the digit, not the letter) immediately
preceding the field width, which indicates that leading zeroes are to be used
instead of leading blanks; and a decimal point followed by a non-negative
integer, which defines the precision (the minimum number of digits of an
integer, or the number of digits following the decimal point of a float).

Some releases of 'printf' may not support all of these modifiers but may also
support others; in case of doubt, check the appropriate documentation and
then experiment.

Examples:
\preverbatim
\begin{verbatim}
     set format y "%t"; set ytics (5,10)          # "5.0" and "1.0"
     set format y "%s"; set ytics (500,1000)      # "500" and "1.0"
     set format y "+-12.3f"; set ytics(12345)     # "+12345.000  "
     set format y "%.2t*10^%+03T"; set ytic(12345)# "1.23*10^+04"
     set format y "%s*10^{%S}"; set ytic(12345)   # "12.345*10^{3}"
     set format y "%s %cg"; set ytic(12345)       # "12.345 kg"
     set format y "%.0P pi"; set ytic(6.283185)   # "2 pi"
     set format y "%.0P%%"; set ytic(50)          # "50%"
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     set log y 2; set format y '%l'; set ytics (1,2,3)
     #displays "1.0", "1.0" and "1.5" (since 3 is 1.5 * 2^1)
\end{verbatim}
\postverbatim

There are some problem cases that arise when numbers like 9.999 are printed
with a format that requires both rounding and a power.

If the data type for the axis is time/date, the format string must contain
valid codes for the 'strftime' function (outside of {\bf gnuplot}, type {\tt"}man
strftime{\tt"}).  See {\bf set timefmt} for a list of the allowed input format codes.
\subsubsection{Time/date specifiers}
In time/date mode, the acceptable formats are:


\begin{center}
\begin{tabular}{|cl|} \hline
\multicolumn{2}{|c|}{Tic-mark label Date/Time Format Specifiers}\\
\hline \hline
Format & Explanation \\ \hline
\verb@%a@ & abbreviated name of day of the week \\
\verb@%A@ & full name of day of the week \\
\verb@%b@ or \verb@%h@ & abbreviated name of the month \\
\verb@%B@ & full name of the month \\
\verb@%d@ & day of the month, 1--31 \\
\verb@%D@ & shorthand for \verb@"%m/%d/%y"@ \\
\verb@%H@ or \verb@%k@ & hour, 0--24 \\
\verb@%I@ or \verb@%l@ & hour, 0--12 \\
\verb@%j@ & day of the year, 1--366 \\
\verb@%m@ & month, 1--12 \\
\verb@%M@ & minute, 0--60 \\
\verb@%p@ & "am" or "pm" \\
\verb@%r@ & shorthand for \verb@"%I:%M:%S %p"@ \\
\verb@%R@ & shorthand for \verb@%H:%M"@ \\
\verb@%S@ & second, 0--60 \\
\verb@%T@ & shorthand for \verb@"%H:%M:%S"@ \\
\verb@%U@ & week of the year (week starts on Sunday) \\
\verb@%w@ & day of the week, 0--6 (Sunday = 0) \\
\verb@%W@ & week of the year (week starts on Monday) \\
\verb@%y@ & year, 0-99 \\
\verb@%Y@ & year, 4-digit \\
\hline
\end{tabular}
\end{center}

Except for the non-numerical formats, these may be preceded by a {\tt"}0{\tt"} ({\tt"}zero{\tt"},
not {\tt"}oh{\tt"}) to pad the field length with leading zeroes, and a positive digit,
to define the minimum field width (which will be overridden if the specified
width is not large enough to contain the number).  There is a 24-character
limit to the length of the printed text; longer strings will be truncated.

Examples:

Suppose the text is {\tt"}76/12/25 23:11:11{\tt"}.  Then
\preverbatim
\begin{verbatim}
     set format x                 # defaults to "12/25/76" \n "23:11"
     set format x "%A, %d %b %Y"  # "Saturday, 25 Dec 1976"
     set format x "%r %d"         # "11:11:11 pm 12/25/76"
\end{verbatim}
\postverbatim

Suppose the text is {\tt"}98/07/06 05:04:03{\tt"}.  Then
\preverbatim
\begin{verbatim}
     set format x "%1y/%2m/%3d %01H:%02M:%03S"  # "98/ 7/  6 5:04:003"
\end{verbatim}
\postverbatim
\subsection{Function style}
The {\bf set function style} command changes the default plotting style for
function plots.

Syntax:
\preverbatim
\begin{verbatim}
     set function style <style-choice>
     show function style
\end{verbatim}
\postverbatim

See {\bf set style} for the choices.  If no choice is given, the choices are
listed.  {\bf show function style} shows the current default function plotting
style.
\subsection{Functions}
The {\bf show functions} command lists all user-defined functions and their
definitions.

Syntax:
\preverbatim
\begin{verbatim}
     show functions
\end{verbatim}
\postverbatim

For information about the definition and usage of functions in {\bf gnuplot},
please see {\bf expressions}.
\subsection{Grid}
The {\bf set grid} command allows grid lines to be drawn on the plot.

Syntax:
\preverbatim
\begin{verbatim}
     set grid {{no}{m}xtics} {{no}{m}ytics} {{no}{m}ztics}
              {{no}{m}x2tics} {{no}{m}y2tics}
              {polar {<angle>}}
              { {linestyle <major_linestyle>}
                | {linetype | lt <major_linetype>}
                  {linewidth | lw <major_linewidth>}
                { , {linestyle | ls <minor_linestyle>}
                    | {linetype | lt <minor_linetype>}
                      {linewidth | lw <minor_linewidth>} } }
     set nogrid
     show grid
\end{verbatim}
\postverbatim

The grid can be enabled and disabled for the major and/or minor tic
marks on any axis, and the linetype and linewidth can be specified
for major and minor grid lines, also via a predefined linestyle, as
far as the active terminal driver supports this.

Additionally, a polar grid can be selected for 2-d plots --- circles are drawn
to intersect the selected tics, and radial lines are drawn at definable
intervals.  (The interval is given in degrees or radians ,depending on the
{\bf set angles} setting.)  Note that a polar grid is no longer automatically
generated in polar mode.

The pertinent tics must be enabled before {\bf set grid} can draw them; {\bf gnuplot}
will quietly ignore instructions to draw grid lines at non-existent tics, but
they will appear if the tics are subsequently enabled.

If no linetype is specified for the minor gridlines, the same linetype as the
major gridlines is used.  The default polar angle is 30 degrees.

By default, grid lines are drawn with half the usual linewidth. The major and
minor linewidth specifiers scale this default value; for example, {\bf set grid
lw .5} will draw grid lines with one quarter the usual linewidth.

Z grid lines are drawn on the back of the plot.  This looks better if a
partial box is drawn around the plot --- see {\bf set border}.
\subsection{Hidden3d}
The {\bf set hidden3d} command enables hidden line removal for surface plotting
(see {\bf splot}).  Some optional features of the underlying algorithm can also
be controlled using this command.

Syntax:
\preverbatim
\begin{verbatim}
     set hidden3d {defaults} |
                  { {{offset <offset>} | {nooffset}}
                    {trianglepattern <bitpattern>}
                    {{undefined <level>} | {noundefined}}
                    {{no}altdiagonal}
                    {{no}bentover} }
     set nohidden3d
     show hidden3d
\end{verbatim}
\postverbatim

In contrast to the usual display in gnuplot, hidden line removal actually
treats the given function or data grids as real surfaces that can't be seen
through, so parts behind the surface will be hidden by it.  For this to be
possible, the surface needs to have 'grid structure' (see {\bf splot datafile}
about this), and it has to be drawn {\bf with lines} or {\bf with linespoints}.

When {\bf hidden3d} is set, both the hidden portion of the surface and possibly
its contours drawn on the base (see {\bf set contour}) as well as the grid will
be hidden.  Each surface has its hidden parts removed with respect to itself
and to other surfaces, if more than one surface is plotted.  Contours drawn
on the surface ({\bf set contour surface}) don't work.  Labels and arrows are
always visible and are unaffected.  The key is also never hidden by the
surface.

Functions are evaluated at isoline intersections.  The algorithm interpolates
linearly between function points or data points when determining the visible
line segments.  This means that the appearance of a function may be different
when plotted with {\bf hidden3d} than when plotted with {\bf nohidden3d} because in
the latter case functions are evaluated at each sample.  Please see {\bf set
samples} and {\bf set isosamples} for discussion of the difference.

The algorithm used to remove the hidden parts of the surfaces has some
additional features controllable by this command.  Specifying {\bf defaults} will
set them all to their default settings, as detailed below.  If {\bf defaults} is
not given, only explicitly specified options will be influenced: all others
will keep their previous values, so you can turn on/off hidden line removal
via {\bf set \{no\}hidden3d}, without modifying the set of options you chose.

The first option, {\bf offset}, influences the linestyle used for lines on the
'back' side.  Normally, they are drawn in a linestyle one index number higher
than the one used for the front, to make the two sides of the surface
distinguishable.  You can specify a different line style offset to add
instead of the default 1, by {\bf offset $<$offset$>$}.  Option {\bf nooffset} stands for
{\bf offset 0}, making the two sides of the surface use the same linestyle.

Next comes the option {\bf trianglepattern $<$bitpattern$>$}.  $<$bitpattern$>$ must be
a number between 0 and 7, interpreted as a bit pattern.  Each bit determines
the visibility of one edge of the triangles each surface is split up into.
Bit 0 is for the 'horizontal' edges of the grid, Bit 1 for the 'vertical'
ones, and Bit 2 for the diagonals that split each cell of the original grid
into two triangles.  The default pattern is 3, making all horizontal and
vertical lines visible, but not the diagonals.  You may want to choose 7 to
see those diagonals as well.

The {\bf undefined $<$level$>$} option lets you decide what the algorithm is to do
with data points that are undefined (missing data, or undefined function
values), or exceed the given x-, y- or z-ranges.  Such points can either be
plotted nevertheless, or taken out of the input data set.  All surface
elements touching a point that is taken out will be taken out as well, thus
creating a hole in the surface.  If $<$level$>$ = 3, equivalent to option
{\bf noundefined}, no points will be thrown away at all.  This may produce all
kinds of problems elsewhere, so you should avoid this.  $<$level$>$ = 2 will
throw away undefined points, but keep the out-of-range ones.  $<$level$>$ = 1,
the default, will get rid of out-of-range points as well.

By specifying {\bf noaltdiagonal}, you can override the default handling of a
special case can occur if {\bf undefined} is active (i.e. $<$level$>$ is not 3).
Each cell of the grid-structured input surface will be divided in two
triangles along one of its diagonals.  Normally, all these diagonals have
the same orientation relative to the grid.  If exactly one of the four cell
corners is excluded by the {\bf undefined} handler, and this is on the usual
diagonal, both triangles will be excluded.  However if the default setting
of {\bf altdiagonal} is active, the other diagonal will be chosen for this cell
instead, minimizing the size of the hole in the surface.

The {\bf bentover} option controls what happens to another special case, this
time in conjunction with the {\bf trianglepattern}.  For rather crumply surfaces,
it can happen that the two triangles a surface cell is divided into are seen
from opposite sides (i.e. the original quadrangle is 'bent over'), as
illustrated in the following ASCII art:

\preverbatim
\begin{verbatim}
                                                             C----B
   original quadrangle:  A--B      displayed quadrangle:     |\   |
     ("set view 0,0")    | /|    ("set view 75,75" perhaps)  | \  |
                         |/ |                                |  \ |
                         C--D                                |   \|
                                                             A    D
\end{verbatim}
\postverbatim

If the diagonal edges of the surface cells aren't generally made visible by
bit 2 of the $<$bitpattern$>$ there, the edge CB above wouldn't be drawn at all,
normally, making the resulting display hard to understand.  Therefore, the
default option of {\bf bentover} will turn it visible in this case.  If you don't
want that, you may choose {\bf nobentover} instead.
\subsection{Isosamples}
The isoline density (grid) for plotting functions as surfaces may be changed
by the {\bf set isosamples} command.

Syntax:
\preverbatim
\begin{verbatim}
     set isosamples <iso_1> {,<iso_2>}
     show isosamples
\end{verbatim}
\postverbatim

Each function surface plot will have $<$iso{\tt\_}1$>$ iso-u lines and $<$iso{\tt\_}2$>$ iso-v
lines.  If you only specify $<$iso{\tt\_}1$>$, $<$iso{\tt\_}2$>$ will be set to the same value
as $<$iso{\tt\_}1$>$.  By default, sampling is set to 10 isolines per u or v axis.
A higher sampling rate will produce more accurate plots, but will take longer.
These parameters have no effect on data file plotting.

An isoline is a curve parameterized by one of the surface parameters while
the other surface parameter is fixed.  Isolines provide a simple means to
display a surface.  By fixing the u parameter of surface s(u,v), the iso-u
lines of the form c(v) = s(u0,v) are produced, and by fixing the v parameter,
the iso-v lines of the form c(u) = s(u,v0) are produced.

When a function surface plot is being done without the removal of hidden
lines, {\bf set samples}  controls the number of points sampled along each
isoline;  see {\bf set samples} and {\bf set hidden3d}.  The contour algorithm
assumes that a function sample occurs at each isoline intersection, so
change in {\bf samples} as well as {\bf isosamples} may be desired when changing
the resolution of a function surface/contour.
\subsection{Key}
The {\bf set key} enables a key (or legend) describing plots on a plot.

The contents of the key, i.e., the names given to each plotted data set and
function and samples of the lines and/or symbols used to represent them, are
determined by the {\bf title} and {\bf with} options of the \{{\bf s}\}{\bf plot} command.
Please see {\bf plot title} and {\bf plot with} for more information.

Syntax:
\preverbatim
\begin{verbatim}
     set key {  left | right | top | bottom | outside | below
              | <position>}
             {Left | Right} {{no}reverse}
             {samplen <sample_length>} {spacing <vertical_spacing>}
             {width <width_increment>}
             {title "<text>"}
             {{no}box { {linestyle | ls <line_style>}
                        | {linetype | lt <line_type>}
                          {linewidth | lw <line_width>}}}
     set nokey
     show key
\end{verbatim}
\postverbatim

By default the key is placed in the upper right corner of the graph.  The
keywords {\bf left}, {\bf right}, {\bf top}, {\bf bottom}, {\bf outside} and {\bf below} may be used
to place the key in the other corners inside the graph or to the right
(outside) or below the graph.  They may be given alone or combined.

Justification of the labels within the key is controlled by {\bf Left} or {\bf Right}
(default is {\bf Right}).  The text and sample can be reversed ({\bf reverse}) and a
box can be drawn around the key ({\bf box \{...\}}) in a specified {\bf linetype}
and {\bf linewidth}, or a user-defined {\bf linestyle}. Note that not all
terminal drivers support linewidth selection, though.

The length of the sample line can be controlled by {\bf samplen}.  The sample
length is computed as the sum of the tic length and $<$sample{\tt\_}length$>$ times the
character width.  {\bf samplen} also affects the positions of point samples in
the key since these are drawn at the midpoint of the sample line, even if it
is not drawn.  $<$sample{\tt\_}length$>$ must be an integer.

The vertical spacing between lines is controlled by {\bf spacing}.  The spacing
is set equal to the product of the pointsize, the vertical tic size, and
$<$vertical{\tt\_}spacing$>$.  The program will guarantee that the vertical spacing is
no smaller than the character height.

The $<$width{\tt\_}increment$>$ is a number of character widths to be added to or
subtracted from the length of the string.  This is useful only when you are
putting a box around the key and you are using control characters in the text.
{\bf gnuplot} simply counts the number of characters in the string when computing
the box width; this allows you to correct it.

A title can be put on the key ({\bf title {\tt"}$<$text$>${\tt"}}) --- see also {\bf syntax} for the
distinction between text in single- or double-quotes.  The key title uses the
same justification as do the plot titles.

The defaults for {\bf set key} are {\bf right}, {\bf top}, {\bf Right}, {\bf noreverse}, {\bf samplen
4}, {\bf spacing 1.25}, {\bf title {\tt"}{\tt"}}, and {\bf nobox}.  The default $<$linetype$>$ is the
same as that used for the plot borders.  Entering {\bf set key} with no options
returns the key to its default configuration.

The $<$position$>$ can be a simple x,y,z as in previous versions, but these can
be preceded by one of four keywords ({\bf first}, {\bf second}, {\bf graph}, {\bf screen})
which selects the coordinate system in which the position is specified.  See
{\bf coordinates} for more details.

The key is drawn as a sequence of lines, with one plot described on each
line.  On the right-hand side (or the left-hand side, if {\bf reverse} is
selected) of each line is a representation that attempts to mimic the way the
curve is plotted.  On the other side of each line is the text description
(the line title), obtained from the {\bf plot} command.  The lines are vertically
arranged so that an imaginary straight line divides the left- and right-hand
sides of the key.  It is the coordinates of the top of this line that are
specified with the {\bf set key} command.  In a {\bf plot}, only the x and y
coordinates are used to specify the line position.  For a {\bf splot}, x, y and
z are all used as a 3-d location mapped using the same mapping as the graph
itself to form the required 2-d screen position of the imaginary line.

Some or all of the key may be outside of the graph boundary, although this
may interfere with other labels and may cause an error on some devices.  If
you use the keywords {\bf outside} or {\bf below}, {\bf gnuplot} makes space for the keys
and the graph becomes smaller.  Putting keys outside to the right, they
occupy as few columns as possible, and putting them below, as many columns as
possible (depending of the length of the labels), thus stealing as little
space from the graph as possible.

When using the TeX or PostScript drivers, or similar drivers where formatting
information is embedded in the string, {\bf gnuplot} is unable to calculate
correctly the width of the string for key positioning.  If the key is to be
positioned at the left, it may be convenient to use the combination  {\bf set key
left Left reverse}.  The box and gap in the grid will be the width of the
literal string.

If {\bf splot} is being used to draw contours, the contour labels will be listed
in the key.  If the alignment of these labels is poor or a different number
of decimal places is desired, the label format can be specified.  See {\bf set
clabel} for details.

Examples:

This places the key at the default location:
\preverbatim
\begin{verbatim}
     set key
\end{verbatim}
\postverbatim

This disables the key:
\preverbatim
\begin{verbatim}
     set nokey
\end{verbatim}
\postverbatim

This places a key at coordinates 2,3.5,2 in the default (first) coordinate
system:
\preverbatim
\begin{verbatim}
     set key 2,3.5,2
\end{verbatim}
\postverbatim

This places the key below the graph:
\preverbatim
\begin{verbatim}
     set key below
\end{verbatim}
\postverbatim

This places the key in the bottom left corner, left-justifies the text,
gives it a title, and draws a box around it in linetype 3:
\preverbatim
\begin{verbatim}
     set key left bottom Left title 'Legend' box 3
\end{verbatim}
\postverbatim
\subsection{Label}
Arbitrary labels can be placed on the plot using the {\bf set label} command.

Syntax:
\preverbatim
\begin{verbatim}
     set label {<tag>} {"<label_text>"} {at <position>}
               {<justification>} {{no}rotate} {font "<name><,size>"}
     set nolabel {<tag>}
     show label
\end{verbatim}
\postverbatim

The $<$position$>$ is specified by either x,y or x,y,z, and may be preceded by
{\bf first}, {\bf second}, {\bf graph}, or {\bf screen} to select the coordinate system.
See {\bf coordinates} for details.

The tag is an integer that is used to identify the label. If no $<$tag$>$ is
given, the lowest unused tag value is assigned automatically.  The tag can be
used to delete or modify a specific label.  To change any attribute of an
existing label, use the {\bf set label} command with the appropriate tag, and
specify the parts of the label to be changed.

By default, the text is placed flush left against the point x,y,z.  To adjust
the way the label is positioned with respect to the point x,y,z, add the
parameter $<$justification$>$, which may be {\bf left}, {\bf right} or {\bf center},
indicating that the point is to be at the left, right or center of the text.
Labels outside the plotted boundaries are permitted but may interfere with
axis labels or other text.

If {\bf rotate} is given, the label is written vertically (if the terminal can do
so, of course).

If one (or more) axis is timeseries, the appropriate coordinate should be
given as a quoted time string according to the {\bf timefmt} format string.  See
{\bf set xdata} and {\bf set timefmt}.

The EEPIC, Imagen, LaTeX, and TPIC drivers allow $\backslash$$\backslash$ in a string to specify
a newline.

Examples:

To set a label at (1,2) to {\tt"}y=x{\tt"}, use:
\preverbatim
\begin{verbatim}
     set label "y=x" at 1,2
\end{verbatim}
\postverbatim

To set a Sigma of size 24, from the Symbol font set, at the center of
the graph, use:
\preverbatim
\begin{verbatim}
     set label "S" at graph 0.5,0.5 center font "Symbol,24"
\end{verbatim}
\postverbatim

To set a label {\tt"}y=x\verb+^+2{\tt"} with the right of the text at (2,3,4), and tag the
label as number 3, use:
\preverbatim
\begin{verbatim}
     set label 3 "y=x^2" at 2,3,4 right
\end{verbatim}
\postverbatim

To change the preceding label to center justification, use:
\preverbatim
\begin{verbatim}
     set label 3 center
\end{verbatim}
\postverbatim

To delete label number 2, use:
\preverbatim
\begin{verbatim}
     set nolabel 2
\end{verbatim}
\postverbatim

To delete all labels, use:
\preverbatim
\begin{verbatim}
     set nolabel
\end{verbatim}
\postverbatim

To show all labels (in tag order), use:
\preverbatim
\begin{verbatim}
     show label
\end{verbatim}
\postverbatim

To set a label on a graph with a timeseries on the x axis, use, for example:
\preverbatim
\begin{verbatim}
     set timefmt "%d/%m/%y,%H:%M"
     set label "Harvest" at "25/8/93",1
\end{verbatim}
\postverbatim
\subsection{Linestyle}
Each terminal has a default set of line and point types, which can be seen
by using the command {\bf test}.  {\bf set linestyle} defines a set of line types
and widths and point types and sizes so that you can refer to them later by
an index instead of repeating all the information at each invocation.

Syntax:
\preverbatim
\begin{verbatim}
     set linestyle <index> {linetype | lt <line_type>}
                           {linewidth | lw <line_width>}
                           {pointtype | pt <point_type>}
                           {pointsize | ps <point_size>}
     set nolinestyle
     show linestyle
\end{verbatim}
\postverbatim

The line and point types are taken from the default types for the terminal
currently in use.  The line width and point size are multipliers for the
default width and size (but note that $<$point{\tt\_}size$>$ here is unaffected by
the multiplier given on 'set pointsize').

The defaults for the line and point types is the index.  The defaults for
the width and size are both unity.

Linestyles created by this mechanism do not replace the default styles;
both may be used.

Not all terminals support the {\bf linewidth} and {\bf pointsize} features; if
not supported, the option will be ignored.

Note that this feature is not completely implemented; linestyles defined by
this mechanism may be used with 'plot', 'splot', 'replot', and 'set arrow',
but not by other commands that allow the default index to be used, such as
'set grid'.

Example:
Suppose that the default lines for indices 1, 2, and 3 are red, green, and
blue, respectively, and the default point shapes for the same indices are a
square, a cross, and a triangle, respectively.  Then

\preverbatim
\begin{verbatim}
     set linestyle 1 lt 2 lw 2 pt 3 ps 0.5
\end{verbatim}
\postverbatim

defines a new linestyle that is green and twice the default width and a new
pointstyle that is a half-sized triangle.  The commands

\preverbatim
\begin{verbatim}
     set function style lines
     plot f(x) lt 3, g(x) ls 1
\end{verbatim}
\postverbatim

will create a plot of f(x) using the default blue line and a plot of g(x)
using the user-defined wide green line.  Similarly the commands

\preverbatim
\begin{verbatim}
     set function style linespoints
     plot p(x) lt 1 pt 3, q(x) ls 1
\end{verbatim}
\postverbatim

will create a plot of f(x) using the default triangles connected by a red
line and q(x) using small triangles connected by a green line.
\subsection{Lmargin}
The command {\bf set lmargin} sets the size of the left margin.  Please see
{\bf set margin} for details.
\subsection{Locale}
The {\bf locale} setting determines the language with which {\bf \{x,y,z\}\{d,m\}tics}
will write the days and months.

Syntax:
\preverbatim
\begin{verbatim}
     set locale {"<locale>"}
\end{verbatim}
\postverbatim

$<$locale$>$ may be any language designation acceptable to your installation.
See your system documentation for the available options.  The default value
is determined from the LANG environment variable.
\subsection{Logscale}
Log scaling may be set on the x, y, z, x2 and/or y2 axes.

Syntax:
\preverbatim
\begin{verbatim}
     set logscale <axes> <base>
     set nologscale <axes>
     show logscale
\end{verbatim}
\postverbatim

where $<$axes$>$ may be any combinations of {\bf x}, {\bf y}, and {\bf z}, in any order, or
{\bf x2} or {\bf y2} and where $<$base$>$ is the base of the log scaling.  If $<$base$>$ is
not given, then 10 is assumed.  If $<$axes$>$ is not given, then all axes are
assumed.  {\bf set nologscale} turns off log scaling for the specified axes.

Examples:

To enable log scaling in both x and z axes:
\preverbatim
\begin{verbatim}
     set logscale xz
\end{verbatim}
\postverbatim

To enable scaling log base 2 of the y axis:
\preverbatim
\begin{verbatim}
     set logscale y 2
\end{verbatim}
\postverbatim

To disable z axis log scaling:
\preverbatim
\begin{verbatim}
     set nologscale z
\end{verbatim}
\postverbatim
\subsection{Mapping}
If data are provided to {\bf splot} in spherical or cylindrical coordinates,
the {\bf set mapping} command should be used to instruct {\bf gnuplot} how to
interpret them.

Syntax:
\preverbatim
\begin{verbatim}
     set mapping {cartesian | spherical | cylindrical}
\end{verbatim}
\postverbatim

A cartesian coordinate system is used by default.

For a spherical coordinate system, the data occupy two or three columns (or
{\bf using} entries).  The first two are interpreted as the polar and azimuthal
angles theta and phi (in the units specified by {\bf set angles}).  The radius r
is taken from the third column if there is one, or is set to unity if there
is no third column.  The mapping is:

\preverbatim
\begin{verbatim}
     x = r * cos(theta) * cos(phi)
     y = r * sin(theta) * cos(phi)
     z = r * sin(phi)
\end{verbatim}
\postverbatim

Note that this is a {\tt"}geographic{\tt"} spherical system, rather than a {\tt"}polar{\tt"} one.

For a cylindrical coordinate system, the data again occupy two or three
columns.  The first two are interpreted as theta (in the units specified by
{\bf set angles}) and z.  The radius is either taken from the third column or set
to unity, as in the spherical case.  The mapping is:

\preverbatim
\begin{verbatim}
     x = r * cos(theta)
     y = r * sin(theta)
     z = z
\end{verbatim}
\postverbatim

The effects of {\bf mapping} can be duplicated with the {\bf using} filter on the
{\bf splot} command, but {\bf mapping} may be more convenient if many data files are
to be processed.  However even if {\bf mapping} is used, {\bf using} may still be
necessary if the data in the file are not in the required order.

{\bf mapping} has no effect on {\bf plot}.
\subsection{Margin}
The computed margins can be overridden by the {\bf set margin} commands.  {\bf show
margin} shows the current settings.

Syntax:
\preverbatim
\begin{verbatim}
     set bmargin {<margin>}
     set lmargin {<margin>}
     set rmargin {<margin>}
     set tmargin {<margin>}
     show margin
\end{verbatim}
\postverbatim

The units of $<$margin$>$ are character heights or widths, as appropriate.  A
positive value defines the absolute size of the margin.  A negative value
(or none) causes {\bf gnuplot} to revert to the computed value.

Normally the margins of a plot are automatically calculated based on tics,
tic labels, axis labels, the plot title, the timestamp and the size of the
key if it is outside the borders.  If, however, tics are attached to the
axes ({\bf set xtics axis}, for example), neither the tics themselves nor their
labels will be included in either the margin calculation or the calculation
of the positions of other text to be written in the margin.  This can lead
to tic labels overwriting other text if the axis is very close to the border.
\subsection{Missing}
The {\bf set missing} command allows you to tell {\bf gnuplot} what character is
used in a data file to denote missing data.

Syntax:
\preverbatim
\begin{verbatim}
     set missing {"<character>"}
     show missing
\end{verbatim}
\postverbatim

Example:
\preverbatim
\begin{verbatim}
     set missing "?"
\end{verbatim}
\postverbatim

would mean that, when plotting a file containing

\preverbatim
\begin{verbatim}
        1 1
        2 ?
        3 2
\end{verbatim}
\postverbatim

the middle line would be ignored.

There is no default character for {\bf missing}.
\subsection{Multiplot}
The command {\bf set multiplot} places {\bf gnuplot} in the multiplot mode, in which
several plots are placed on the same page, window, or screen.

Syntax:
\preverbatim
\begin{verbatim}
     set multiplot
     set nomultiplot
\end{verbatim}
\postverbatim

For some terminals, no plot is displayed until the command {\bf set nomultiplot}
is given, which causes the entire page to be drawn and then returns {\bf gnuplot}
to its normal single-plot mode.  For other terminals, each separate {\bf plot}
command produces a plot, but the screen may not be cleared between plots.

Any labels or arrows that have been defined will be drawn for each plot
according to the current size and origin (unless their coordinates are
defined in the {\bf screen} system).  Just about everything else that can be
{\bf set} is applied to each plot, too.  If you want something to appear only
once on the page, for instance a single time stamp, you'll need to put a {\bf set
time}/{\bf set notime} pair around one of the {\bf plot}, {\bf splot} or {\bf replot}
commands within the {\bf set multiplot}/{\bf set nomultiplot} block.

The commands {\bf set origin} and {\bf set size} must be used to correctly position
each plot; see {\bf set origin} and {\bf set size} for details of their usage.

Example:
\preverbatim
\begin{verbatim}
     set size 0.7,0.7
     set origin 0.1,0.1
     set multiplot
     set size 0.4,0.4
     set origin 0.1,0.1
     plot sin(x)
     set size 0.2,0.2
     set origin 0.5,0.5
     plot cos(x)
     set nomultiplot
\end{verbatim}
\postverbatim

displays a plot of cos(x) stacked above a plot of sin(x).  Note the initial
{\bf set size} and {\bf set origin}.  While these are not always required, their
inclusion is recommended.  Some terminal drivers require that bounding box
information be available before any plots can be made, and the form given
above guarantees that the bounding box will include the entire plot array
rather than just the bounding box of the first plot.

{\bf set size} and {\bf set origin} refer to the entire plotting area used for each
plot.  If you want to have the axes themselves line up, you can guarantee
that the margins are the same size with the {\bf set margin} commands.  See
{\bf set margin} for their use.  Note that the margin settings are absolute,
in character units, so the appearance of the graph in the remaining space
will depend on the screen size of the display device, e.g., perhaps quite
different on a video display and a printer.
\subsection{Mx2tics}
Minor tic marks along the x2 (top) axis are controlled by {\bf set mx2tics}.
Please see {\bf set mxtics}.
\subsection{Mxtics}
Minor tic marks along the x axis are controlled by {\bf set mxtics}.  They can be
turned off with {\bf set nomxtics}.  Similar commands control minor tics along
the other axes.

Syntax:
\preverbatim
\begin{verbatim}
     set mxtics {<freq> | default}
     set nomxtics
     show mxtics
\end{verbatim}
\postverbatim

The same syntax applies to {\bf mytics}, {\bf mztics}, {\bf mx2tics} and {\bf my2tics}.

$<$freq$>$ is the number of sub-intervals (NOT the number of minor tics) between
major tics (ten is the default for a linear axis, so there are nine minor
tics between major tics). Selecting {\bf default} will return the number of minor
ticks to its default value.

If the axis is logarithmic, the number of sub-intervals will be set to a
reasonable number by default (based upon the length of a decade).  This will
be overridden if $<$freq$>$ is given.  However the usual minor tics (2, 3, ...,
8, 9 between 1 and 10, for example) are obtained by setting $<$freq$>$ to 10,
even though there are but nine sub-intervals.

Minor tics can be used only with uniformly spaced major tics.  Since major
tics can be placed arbitrarily by {\bf set \{x$|$x2$|$y$|$y2$|$z\}tics}, minor tics cannot
be used if major tics are explicitly {\bf set}.

By default, minor tics are off for linear axes and on for logarithmic axes.
They inherit the settings for {\bf axis$|$border} and {\bf \{no\}mirror} specified for
the major tics.  Please see {\bf set xtics} for information about these.
\subsection{My2tics}
Minor tic marks along the y2 (right-hand) axis are controlled by {\bf set
my2tics}.  Please see {\bf set mxtics}.
\subsection{Mytics}
Minor tic marks along the y axis are controlled by {\bf set mytics}.  Please
see {\bf set mxtics}.
\subsection{Mztics}
Minor tic marks along the z axis are controlled by {\bf set mztics}.  Please
see {\bf set mxtics}.
\subsection{Offsets}
Offsets provide a mechanism to put a boundary around the data inside of an
autoscaled graph.

Syntax:
\preverbatim
\begin{verbatim}
     set offsets <left>, <right>, <top>, <bottom>
     set nooffsets
     show offsets
\end{verbatim}
\postverbatim

Each offset may be a constant or an expression.  Each defaults to 0.  Left
and right offsets are given in units of the x axis, top and bottom offsets in
units of the y axis.  A positive offset expands the graph in the specified
direction, e.g., a positive bottom offset makes ymin more negative.  Negative
offsets, while permitted, can have unexpected interactions with autoscaling
and clipping.

Offsets are ignored in {\bf splot}s.

Example:
\preverbatim
\begin{verbatim}
     set offsets 0, 0, 2, 2
     plot sin(x)
\end{verbatim}
\postverbatim

This graph of sin(x) will have a y range [-3:3] because the function
will be autoscaled to [-1:1] and the vertical offsets are each two.
\subsection{Origin}
The {\bf set origin} command is used to specify the origin of a plotting surface
(i.e., the graph and its margins) on the screen.  The coordinates are given
in the {\bf screen} coordinate system (see {\bf coordinates} for information about
this system).

Syntax:
\preverbatim
\begin{verbatim}
     set origin <x-origin>,<y-origin>
\end{verbatim}
\postverbatim
\subsection{Output}
By default, screens are displayed to the standard output. The {\bf set output}
command redirects the display to the specified file or device.

Syntax:
\preverbatim
\begin{verbatim}
     set output {"<filename>"}
     show output
\end{verbatim}
\postverbatim

The filename must be enclosed in quotes.  If the filename is omitted, any
output file opened by a previous invocation of {\bf set output} will be closed
and new output will be sent to STDOUT.  (If you give the command {\bf set output
{\tt"}STDOUT{\tt"}}, your output may be sent to a file named {\tt"}STDOUT{\tt"}!  [{\tt"}May be{\tt"}, not
{\tt"}will be{\tt"}, because some terminals, like {\bf x11}, ignore {\bf set output}.])

MSDOS users should note that the $\backslash$ character has special significance in
double-quoted strings, so single-quotes should be used for filenames in
different directories.

When both {\bf set terminal} and {\bf set output} are used together, it is safest to
give {\bf set terminal} first, because some terminals set a flag which is needed
in some operating systems.  This would be the case, for example, if the
operating system needs to know whether or not a file is to be formatted in
order to open it properly.

On machines with popen functions (Unix), output can be piped through a shell
command if the first non-whitespace character of the filename is '$|$'.
For instance,

\preverbatim
\begin{verbatim}
     set output "|lpr -Plaser filename"
     set output "|lp -dlaser filename"
\end{verbatim}
\postverbatim

On MSDOS machines, {\bf set output {\tt"}PRN{\tt"}} will direct the output to the default
printer.  On VMS, output can be sent directly to any spooled device.  It is
also possible to send the output to DECnet transparent tasks, which allows
some flexibility.
\subsection{Parametric}
The {\bf set parametric} command changes the meaning of {\bf plot} ({\bf splot}) from
normal functions to parametric functions.  The command {\bf set noparametric}
restores the plotting style to normal, single-valued expression plotting.

Syntax:
\preverbatim
\begin{verbatim}
     set parametric
     set noparametric
     show parametric
\end{verbatim}
\postverbatim

For 2-d plotting, a parametric function is determined by a pair of parametric
functions operating on a parameter.  An example of a 2-d parametric function
would be {\bf plot sin(t),cos(t)}, which draws a circle (if the aspect ratio is
set correctly --- see {\bf set size}).  {\bf gnuplot} will display an error message if
both functions are not provided for a parametric {\bf plot}.

For 3-d plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v).
Therefore a triplet of functions is required.  An example of a 3-d parametric
function would be {\bf cos(u)*cos(v),cos(u)*sin(v),sin(u)}, which draws a sphere.
{\bf gnuplot} will display an error message if all three functions are not
provided for a parametric {\bf splot}.

The total set of possible plots is a superset of the simple f(x) style plots,
since the two functions can describe the x and y values to be computed
separately.  In fact, plots of the type t,f(t) are equivalent to those
produced with f(x) because the x values are computed using the identity
function.  Similarly, 3-d plots of the type u,v,f(u,v) are equivalent to
f(x,y).

Note that the order the parametric functions are specified is xfunction,
yfunction (and zfunction) and that each operates over the common parametric
domain.

Also, the {\bf set parametric} function implies a new range of values.  Whereas
the normal f(x) and f(x,y) style plotting assume an xrange and yrange (and
zrange), the parametric mode additionally specifies a trange, urange, and
vrange.  These ranges may be set directly with {\bf set trange}, {\bf set urange},
and {\bf set vrange}, or by specifying the range on the {\bf plot} or {\bf splot}
commands.  Currently the default range for these parametric variables is
[-5:5].  Setting the ranges to something more meaningful is expected.
\subsection{Pointsize}
The {\bf set pointsize} command scales the size of the points used in plots.

Syntax:
\preverbatim
\begin{verbatim}
     set pointsize <multiplier>
     show pointsize
\end{verbatim}
\postverbatim

The default is a multiplier of 1.0.  Larger pointsizes may be useful to
make points more visible in bitmapped graphics.

The pointsize of a single plot may be changed on the {\bf plot} command.  See
{\bf plot with} for details.

Please note that the pointsize setting is not supported by all terminal
types.
\subsection{Polar}
The {\bf set polar} command changes the meaning of the plot from rectangular
coordinates to polar coordinates.

Syntax:
\preverbatim
\begin{verbatim}
     set polar
     set nopolar
     show polar
\end{verbatim}
\postverbatim

There have been changes made to polar mode in version 3.7, so that scripts
for {\bf gnuplot} versions 3.5 and earlier will require modification.  The main
change is that the dummy variable t is used for the angle so that the x and
y ranges can be controlled independently.  Other changes are:
1) tics are no longer put along the zero axes automatically
 --- use {\bf set xtics axis nomirror}; {\bf set ytics axis nomirror};
2) the grid, if selected, is not automatically polar
 --- use {\bf set grid polar};
3) the grid is not labelled with angles
 --- use {\bf set label} as necessary.

In polar coordinates, the dummy variable (t) is an angle.  The default range
of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see
{\bf set angles}).

The command {\bf set nopolar} changes the meaning of the plot back to the default
rectangular coordinate system.

The {\bf set polar} command is not supported for {\bf splot}s.  See the {\bf set mapping}
command for similar functionality for {\bf splot}s.

While in polar coordinates the meaning of an expression in t is really
r = f(t), where t is an angle of rotation.  The trange controls the domain
(the angle) of the function, and the x and y ranges control the range of the
graph in the x and y directions.  Each of these ranges, as well as the
rrange, may be autoscaled or set explicitly.  See {\bf set xrange} for details
of all the {\bf set range} commands.

Example:
\preverbatim
\begin{verbatim}
     set polar
     plot t*sin(t)
     plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)
\end{verbatim}
\postverbatim

The first {\bf plot} uses the default polar angular domain of 0 to 2*pi.  The
radius and the size of the graph are scaled automatically.  The second {\bf plot}
expands the domain, and restricts the size of the graph to [-3:3] in both
directions.

You may want to {\bf set size square} to have {\bf gnuplot} try to make the aspect
ratio equal to unity, so that circles look circular.
\subsection{Rmargin}
The command {\bf set rmargin} sets the size of the right margin.  Please see
{\bf set margin} for details.
\subsection{Rrange}
The {\bf set rrange} command sets the range of the radial coordinate for a
graph in polar mode.  Please see {\bf set xrange} for details.
\subsection{Samples}
The sampling rate of functions, or for interpolating data, may be changed
by the {\bf set samples} command.

Syntax:
\preverbatim
\begin{verbatim}
     set samples <samples_1> {,<samples_2>}
     show samples
\end{verbatim}
\postverbatim

By default, sampling is set to 100 points.  A higher sampling rate will
produce more accurate plots, but will take longer.  This parameter has no
effect on data file plotting unless one of the interpolation/approximation
options is used.  See {\bf plot smooth} re 2-d data and {\bf set cntrparam} and
{\bf set dgrid3d} re 3-d data.

When a 2-d graph is being done, only the value of $<$samples{\tt\_}1$>$ is relevant.

When a surface plot is being done without the removal of hidden lines, the
value of samples specifies the number of samples that are to be evaluated for
the isolines.  Each iso-v line will have $<$sample{\tt\_}1$>$ samples and each iso-u
line will have $<$sample{\tt\_}2$>$ samples.  If you only specify $<$samples{\tt\_}1$>$,
$<$samples{\tt\_}2$>$ will be set to the same value as $<$samples{\tt\_}1$>$.  See also {\bf set
isosamples}.
\subsection{Size}
The {\bf set size} command scales the displayed size of the plot.

Syntax:
\preverbatim
\begin{verbatim}
     set size {{no}square | ratio <r> | noratio} {<xscale>,<yscale>}
     show size
\end{verbatim}
\postverbatim

The $<$xscale$>$ and $<$yscale$>$ values are the scaling factors for the size of the
plot, which includes the graph and the margins.

{\bf ratio} causes {\bf gnuplot} to try to create a graph with an aspect ratio of $<$r$>$
(the ratio of the y-axis length to the x-axis length) within the portion of
the plot specified by $<$xscale$>$ and $<$yscale$>$.

The meaning of a negative value for $<$r$>$ is different.  If $<$r$>$=-1, gnuplot
tries to set the scales so that the unit has the same length on both the x
and y axes (suitable for geographical data, for instance).  If $<$r$>$=-2, the
unit on y has twice the length of the unit on x, and so on.

The success of {\bf gnuplot} in producing the requested aspect ratio depends on
the terminal selected.  The graph area will be the largest rectangle of
aspect ratio $<$r$>$ that will fit into the specified portion of the output
(leaving adequate margins, of course).

{\bf square} is a synonym for {\bf ratio 1}.

Both {\bf noratio} and {\bf nosquare} return the graph to the default aspect ratio
of the terminal, but do not return $<$xscale$>$ or $<$yscale$>$ to their default
values (1.0).

{\bf ratio} and {\bf square} have no effect on 3-d plots.

{\bf set size} is relative to the default size, which differs from terminal to
terminal.  Since {\bf gnuplot} fills as much of the available plotting area as
possible by default, it is safer to use {\bf set size} to decrease the size of
a plot than to increase it.  See {\bf set terminal} for the default sizes.

On some terminals, changing the size of the plot will result in text being
misplaced.

Examples:

To set the size to normal size use:
\preverbatim
\begin{verbatim}
     set size 1,1
\end{verbatim}
\postverbatim

To make the graph half size and square use:
\preverbatim
\begin{verbatim}
     set size square 0.5,0.5
\end{verbatim}
\postverbatim

To make the graph twice as high as wide use:
\preverbatim
\begin{verbatim}
     set size ratio 2
\end{verbatim}
\postverbatim

\subsection{Style}
Default styles are chosen with the {\bf set function style} and {\bf set data style}
commands.  See {\bf plot with} for information about how to override the default
plotting style for individual functions and data sets.

Syntax:
\preverbatim
\begin{verbatim}
     set function style <style>
     set data style <style>
     show function style
     show data style
\end{verbatim}
\postverbatim

The types used for all line and point styles (i.e., solid, dash-dot, color,
etc. for lines; circles, squares, crosses, etc. for points) will be either
those specified on the {\bf plot} or {\bf splot} command or will be chosen
sequentially from the types available to the terminal in use.  Use the
command {\bf test} to see what is available.

None of the styles requiring more than two columns of information (e.g.,
{\bf errorbars}) can be used with {\bf splot}s or function {\bf plot}s.  Neither {\bf boxes}
nor any of the {\bf steps} styles can be used with {\bf splot}s.  If an inappropriate
style is specified, it will be changed to {\bf points}.

For 2-d data with more than two columns, {\bf gnuplot} is picky about the allowed
{\bf errorbar} styles.  The {\bf using} option on the {\bf plot} command can be used to
set up the correct columns for the style you want.  (In this discussion,
{\tt"}column{\tt"} will be used to refer both to a column in the data file and an entry
in the {\bf using} list.)

For three columns, only {\bf xerrorbars}, {\bf yerrorbars} (or {\bf errorbars}), {\bf boxes},
and {\bf boxerrorbars} are allowed.  If another plot style is used, the style
will be changed to {\bf yerrorbars}.  The {\bf boxerrorbars} style will calculate the
boxwidth automatically.

For four columns, only {\bf xerrorbars}, {\bf yerrorbars} (or {\bf errorbars}),
{\bf xyerrorbars}, {\bf boxxyerrorbars}, and {\bf boxerrorbars} are allowed.  An illegal
style will be changed to {\bf yerrorbars}.

Five-column data allow only the {\bf boxerrorbars}, {\bf financebars}, and
{\bf candlesticks} styles.  (The last two of these are primarily used for plots
of financial prices.)  An illegal style will be changed to {\bf boxerrorbars}
before plotting.

Six- and seven-column data only allow the {\bf xyerrorbars} and {\bf boxxyerrorbars}
styles.  Illegal styles will be changed to {\bf xyerrorbars} before plotting.

For more information about error bars, please see {\bf plot errorbars}.
\subsubsection{Boxerrorbars}
The {\bf boxerrorbars} style is only relevant to 2-d data plotting.  It is a
combination of the {\bf boxes} and {\bf yerrorbars} styles.  The boxwidth will come
from the fourth column if the y errors are in the form of {\tt"}ydelta{\tt"} and the
boxwidth was not previously set equal to -2.0 ({\bf set boxwidth -2.0}) or from
the fifth column if the y errors are in the form of {\tt"}ylow yhigh{\tt"}.  The
special case  {\bf boxwidth = -2.0} is for four-column data with y errors in the
form {\tt"}ylow yhigh{\tt"}.  In this case the boxwidth will be calculated so that each
box touches the adjacent boxes.  The width will also be calculated in cases
where three-column data are used.

The box height is determined from the y error in the same way as it is for
the {\bf yerrorbars} style --- either from y-ydelta to y+ydelta or from ylow to
yhigh, depending on how many data columns are provided.
\subsubsection{Boxes}
The {\bf boxes} style is only relevant to 2-d plotting.  It draws a box centered
about the given x coordinate from the x axis (not the graph border) to the
given y coordinate.  The width of the box is obtained in one of three ways.
If it is a data plot and the data file has a third column, this will be used
to set the width of the box.  If not, if a width has been set using the {\bf set
boxwidth} command, this will be used.  If neither of these is available, the
width of each box will be calculated automatically so that it touches the
adjacent boxes.
\subsubsection{Boxxyerrorbars}
The {\bf boxxyerrorbars} style is only relevant to 2-d data plotting.  It is a
combination of the {\bf boxes} and {\bf xyerrorbars} styles.

The box width and height are determined from the x and y errors in the same
way as they are for the {\bf xyerrorbars} style --- either from xlow to xhigh and
from ylow to yhigh, or from x-xdelta to x+xdelta and from y-ydelta to
y+ydelta , depending on how many data columns are provided.
\subsubsection{Candlesticks}
The {\bf candlesticks} style is only relevant for 2-d data plotting of financial
data.  Five columns of data are required; in order, these should be the x
coordinate (most likely a date) and the opening, low, high, and closing
prices.  The symbol is an open rectangle, centered horizontally at the x
coordinate and limited vertically by the opening and closing prices.  A
vertical line segment at the x coordinate extends up from the top of the
rectangle to the high price and another down to the low.  The width of the
rectangle may be changed by {\bf set bar}.  The symbol will be unchanged if the
low and high prices are interchanged or if the opening and closing prices
are interchanged.  See {\bf set bar} and {\bf financebars}.
\subsubsection{Dots}
The {\bf dots} style plots a tiny dot at each point; this is useful for scatter
plots with many points.
\subsubsection{Financebars}
The {\bf financebars} style is only relevant for 2-d data plotting of financial
data.  Five columns of data are required; in order, these should be the x
coordinate (most likely a date) and the opening, low, high, and closing
prices.  The symbol is a vertical line segment, located horizontally at the x
coordinate and limited vertically by the high and low prices.  A horizontal
tic on the left marks the opening price and one on the right marks the
closing price.  The length of these tics may be changed by {\bf set bar}.  The
symbol will be unchanged if the high and low prices are interchanged.  See
{\bf set bar} and {\bf candlesticks}.
\subsubsection{Fsteps}
The {\bf fsteps} style is only relevant to 2-d plotting.  It connects consecutive
points with two line segments: the first from (x1,y1) to (x1,y2) and the
second from (x1,y2) to (x2,y2).
\subsubsection{Histeps}
The {\bf histeps} style is only relevant to 2-d plotting.  It is intended for
plotting histograms.  Y-values are assumed to be centered at the x-values;
the point at x1 is represented as a horizontal line from ((x0+x1)/2,y1) to
((x1+x2)/2,y1).  The lines representing the end points are extended so that
the step is centered on at x.  Adjacent points are connected by a vertical
line at their average x, that is, from ((x1+x2)/2,y1) to ((x1+x2)/2,y2).

If {\bf autoscale} is in effect, it selects the xrange from the data rather than
the steps, so the end points will appear only half as wide as the others.

{\bf histeps} is only a plotting style; {\bf gnuplot} does not have the ability to
create bins and determine their population from some data set.
\subsubsection{Impulses}
The {\bf impulses} style displays a vertical line from the x axis (not the graph
border), or from the grid base for {\bf splot}, to each point.
\subsubsection{Lines}
The {\bf lines} style connects adjacent points with straight line segments.
\subsubsection{Linespoints}
The {\bf linespoints} style does both {\bf lines} and {\bf points}, that is, it draws a
small symbol at each point and then connects adjacent points with straight
line segments.  The command {\bf set pointsize} may be used to change the size of
the points.  See {\bf set pointsize} for its usage.

{\bf linespoints} may be abbreviated {\bf lp}.
\subsubsection{Points}
The {\bf points} style displays a small symbol at each point.  The command {\bf set
pointsize} may be used to change the size of the points.  See {\bf set pointsize}
for its usage.
\subsubsection{Steps}
The {\bf steps} style is only relevant to 2-d plotting.  It connects consecutive
points with two line segments: the first from (x1,y1) to (x2,y1) and the
second from (x2,y1) to (x2,y2).
\subsubsection{Vector}
The {\bf vector} style draws a vector from (x,y) to (x+xdelta,y+ydelta).  Thus
it requires four columns of data.  It also draws a small arrowhead at the
end of the vector.

The {\bf vector} style is still experimental: it doesn't get clipped properly
and other things may also be wrong with it.  Use it at your own risk.
\subsubsection{Xerrorbars}
The {\bf xerrorbars} style is only relevant to 2-d data plots.  {\bf xerrorbars} is
like {\bf dots}, except that a horizontal error bar is also drawn.  At each point
(x,y), a line is drawn from (xlow,y) to (xhigh,y) or from (x-xdelta,y) to
(x+xdelta,y), depending on how many data columns are provided.  A tic mark
is placed at the ends of the error bar (unless {\bf set bar} is used --- see {\bf set
bar} for details).
\subsubsection{Xyerrorbars}
The {\bf xyerrorbars} style is only relevant to 2-d data plots.  {\bf xyerrorbars} is
like {\bf dots}, except that horizontal and vertical error bars are also drawn.
At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and
from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from
(xlow,y) to (xhigh,y), depending upon the number of data columns provided.  A
tic mark is placed at the ends of the error bar (unless {\bf set bar} is
used --- see {\bf set bar} for details).

If data are provided in an unsupported mixed form, the {\bf using} filter on the
{\bf plot} command should be used to set up the appropriate form.  For example,
if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use

\preverbatim
\begin{verbatim}
     plot 'data' using 1:2:($1-$3),($1+$3),4,5 with xyerrorbars
\end{verbatim}
\postverbatim
\subsubsection{Yerrorbars}
The {\bf yerrorbars} (or {\bf errorbars}) style is only relevant to 2-d data plots.
{\bf yerrorbars} is like {\bf dots}, except that a vertical error bar is also drawn.
At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or
from (x,ylow) to (x,yhigh), depending on how many data columns are provided.
A tic mark is placed at the ends of the error bar (unless {\bf set bar} is
used --- see {\bf set bar} for details).
\subsection{Surface}
The command {\bf set surface} controls the display of surfaces by {\bf splot}.

Syntax:
\preverbatim
\begin{verbatim}
     set surface
     set nosurface
     show surface
\end{verbatim}
\postverbatim

The surface is drawn with the style specifed by {\bf with}, or else the
appropriate style, data or function.

Whenever {\bf set nosurface} is issued, {\bf splot} will not draw points or lines
corresponding to the function or data file points.  Contours may be still be
drawn on the surface, depending on the {\bf set contour} option. {\bf set nosurface;
set contour base} is useful for displaying contours on the grid base.  See
also {\bf set contour}.
\subsection{Terminal}
{\bf gnuplot} supports many different graphics devices.  Use {\bf set terminal} to
tell {\bf gnuplot} what kind of output to generate. Use {\bf set output} to redirect
that output to a file or device.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal {<terminal-type>}
     show terminal
\end{verbatim}
\postverbatim

If $<$terminal-type$>$ is omitted, {\bf gnuplot} will list the available terminal
types.  $<$terminal-type$>$ may be abbreviated.

If both {\bf set terminal} and {\bf set output} are used together, it is safest to
give {\bf set terminal} first, because some terminals set a flag which is needed
in some operating systems.

Several terminals have additional options.  For example, see {\bf dumb},
{\bf iris4d}, {\bf hpljii} or {\bf postscript}.

This document may describe drivers that are not available to you because they
were not installed, or it may not describe all the drivers that are available
to you, depending on its output format.
\subsubsection{Aed767}
The {\bf aed512} and {\bf aed767} terminal drivers support AED graphics terminals.
The two drivers differ only in their horizontal ranges, which are 512 and
768 pixels, respectively.  Their vertical range is 575 pixels.  There are
no options for these drivers.
\subsubsection{Aifm}
Several options may be set in {\bf aifm} --- the Adobe Illustrator 3.0+ driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal aifm {<color>} {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

$<$color$>$ is either {\bf color} or {\bf monochrome}; {\tt"}$<$fontname$>${\tt"} is the name of a
valid PostScript font; $<$fontsize$>$ is the size of the font in PostScript
points, before scaling by the {\bf set size} command.  Selecting {\bf default} sets
all options to their default values: {\bf monochrome}, {\tt"}Helvetica{\tt"}, and 14pt.

Since AI does not really support multiple pages, multiple graphs will be
drawn directly on top of one another.  However, each graph will be grouped
individually, making it easy to separate them inside AI (just pick them up
and move them).

Examples:
\preverbatim
\begin{verbatim}
     set term aifm
     set term aifm 22
     set size 0.7,1.4; set term aifm color "Times-Roman" 14
\end{verbatim}
\postverbatim
\subsubsection{Amiga}
The {\bf amiga} terminal, for Commodore Amiga computers, allows the user to
plot either to a screen (default), or, if Kickstart 3.0 or higher is
installed, to a window on the current public screen. The font and its size
can also be selected.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal amiga {screen | window} {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

The default font is 8-point {\tt"}topaz{\tt"}.

The screen option uses a virtual screen, so it is possible that the graph
will be larger than the screen.
\subsubsection{Apollo}
The {\bf apollo} terminal driver supports the Apollo Graphics Primitive Resource
with rescaling after window resizing.  It has no options.

If a fixed-size window is desired, the {\bf gpr} terminal may be used instead.
\subsubsection{Atari ST (via AES)}
The {\bf atari} terminal has options to set the character size and the screen
colors.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal atari {<fontsize>} {<col0> <col1> ... <col15.}
\end{verbatim}
\postverbatim

The character size must appear if any colors are to be specified.  Each of
the (up to 16) colors is given as a three-digit hex number, where the digits
represent RED, GREEN and BLUE (in that order).  The range of 0--15 is scaled
to whatever color range the screen actually has.  On a normal ST screen, odd
and even intensities are the same.

Examples:
\preverbatim
\begin{verbatim}
     set terminal atari 4    # use small (6x6) font
     set terminal atari 6 0  # set monochrome screen to white on black
     set terminal atari 13 0 fff f00 f0 f ff f0f
                # set first seven colors to black, white, green, blue,
                # cyan, purple, and yellow and use large font (8x16).
\end{verbatim}
\postverbatim

Additionally, if an environment variable GNUCOLORS exists, its contents are
interpreted as an options string, but an explicit terminal option takes
precedence.
\subsubsection{Atari ST (via VDI)}
The {\bf vdi} terminal is the same as the {\bf atari} terminal, except that it sends
output to the screen via the VDI and not into AES-Windows.

The {\bf vdi} terminal has options to set the character size and the screen
colors.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal vdi {<fontsize>} {<col0> <col1> ... <col15.}
\end{verbatim}
\postverbatim

The character size must appear if any colors are to be specified.  Each of
the (up to 16) colors is given as a three-digit hex number, where the digits
represent RED, GREEN and BLUE (in that order).  The range of 0--15 is scaled
to whatever color range the screen actually has.  On a normal ST screen, odd
and even intensities are the same.

Examples:
\preverbatim
\begin{verbatim}
     set terminal vdi 4    # use small (6x6) font
     set terminal vdi 6 0  # set monochrome screen to white on black
     set terminal vdi 13 0 fff f00 f0 f ff f0f
                # set first seven colors to black, white, green, blue,
                # cyan, purple, and yellow and use large font (8x16).
\end{verbatim}
\postverbatim

Additionally, if an environment variable GNUCOLORS exists, its contents are
interpreted as an options string, but an explicit terminal option takes
precedence.
\subsubsection{Be}
{\bf gnuplot} provides the {\bf be} terminal type for use with X servers.  This
terminal type is set automatically at startup if the {\bf DISPLAY} environment
variable is set, if the {\bf TERM} environment variable is set to {\bf xterm}, or
if the {\bf -display} command line option is used.

Syntax:
\preverbatim
\begin{verbatim}
         set terminal be {reset} {<n>}
\end{verbatim}
\postverbatim

Multiple plot windows are supported: {\bf set terminal be $<$n$>$} directs the
output to plot window number n.  If n$>$0, the terminal number will be
appended to the window title and the icon will be labeled {\bf gplt $<$n$>$}.
The active window may distinguished by a change in cursor (from default
to crosshair.)

Plot windows remain open even when the {\bf gnuplot} driver is changed to a
different device.  A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing {\bf close} from a window
manager menu.  All plot windows can be closed by specifying {\bf reset}, which
actually terminates the subprocess which maintains the windows (unless
{\bf -persist} was specified).

Plot windows will automatically be closed at the end of the session
unless the {\bf -persist} option was given.

The size or aspect ratio of a plot may be changed by resizing the {\bf gnuplot}
window.

Linewidths and pointsizes may be changed from within {\bf gnuplot} with
{\bf set linestyle}.

For terminal type {\bf be}, {\bf gnuplot} accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file.  See the X(1) man page
(or its equivalent) for a description of such options.

A number of other {\bf gnuplot} options are available for the {\bf be} terminal.
These may be specified either as command-line options when {\bf gnuplot} is
invoked or as resources in the configuration file {\tt"}/.Xdefaults{\tt"}.  They are
set upon initialization and cannot be altered during a {\bf gnuplot} session.
\subsubsubsection{Command-line{\tt\_}options}
In addition to the X Toolkit options, the following options may be specified
on the command line when starting {\bf gnuplot} or as resources in your
{\tt"}.Xdefaults{\tt"} file:

\begin{center}
\begin{tabular}{|cl|} \hline
`-mono`  & forces monochrome rendering on color displays.\\
`-gray`  & requests grayscale rendering on grayscale or color displays.\\
                 & (Grayscale displays receive monochrome rendering by default.) \\
`-clear` & requests that the window be cleared momentarily before a\\
                 & new plot is displayed. \\
`-tvtwm` & requests that geometry specifications for position of the\\
                 & window be made relative to the currently displayed portion\\
                 & of the virtual root. \\
`-raise` & raise plot window after each plot. \\
`-noraise` & do not raise plot window after each plot. \\
`-persist`&plot windows survive after main gnuplot program exits. \\
\hline
\end{tabular}
\end{center}
The options are shown above in their command-line syntax.  When entered as
resources in {\tt"}.Xdefaults{\tt"}, they require a different syntax.

Example:
\preverbatim
\begin{verbatim}
         gnuplot*gray: on
\end{verbatim}
\postverbatim

{\bf gnuplot} also provides a command line option ({\bf -pointsize $<$v$>$}) and a
resource, {\bf gnuplot*pointsize: $<$v$>$}, to control the size of points plotted
with the {\bf points} plotting style.  The value {\bf v} is a real number (greater
than 0 and less than or equal to ten) used as a scaling factor for point
sizes.  For example, {\bf -pointsize 2} uses points twice the default size, and
{\bf -pointsize 0.5} uses points half the normal size.
\subsubsubsection{Monochome{\tt\_}options}
For monochrome displays, {\bf gnuplot} does not honor foreground or background
colors.  The default is black-on-white.  {\bf -rv} or {\bf gnuplot*reverseVideo: on}
requests white-on-black.

\subsubsubsection{Color{\tt\_}resources}
For color displays, {\bf gnuplot} honors the following resources (shown here
with their default values) or the greyscale resources.  The values may be
color names as listed in the BE rgb.txt file on your system, hexadecimal
RGB color specifications (see BE documentation), or a color name followed
by a comma and an {\bf intensity} value from 0 to 1.  For example, {\bf blue, 0.5}
means a half intensity blue.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*background: white\\
&gnuplot*textColor: black\\
&gnuplot*borderColor: black\\
&gnuplot*axisColor: black\\
&gnuplot*line1Color: red\\
&gnuplot*line2Color: green\\
&gnuplot*line3Color: blue\\
&gnuplot*line4Color: magenta\\
&gnuplot*line5Color: cyan\\
&gnuplot*line6Color: sienna\\
&gnuplot*line7Color: orange\\
&gnuplot*line8Color: coral\\
\hline
\end{tabular}
\end{center}

The command-line syntax for these is, for example,

Example:
\preverbatim
\begin{verbatim}
         gnuplot -background coral
\end{verbatim}
\postverbatim

\subsubsubsection{Grayscale{\tt\_}resources}
When {\bf -gray} is selected, {\bf gnuplot} honors the following resources for
grayscale or color displays (shown here with their default values).  Note
that the default background is black.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*background: black\\
&gnuplot*textGray: white\\
&gnuplot*borderGray: gray50\\
&gnuplot*axisGray: gray50\\
&gnuplot*line1Gray: gray100\\
&gnuplot*line2Gray: gray60\\
&gnuplot*line3Gray: gray80\\
&gnuplot*line4Gray: gray40\\
&gnuplot*line5Gray: gray90\\
&gnuplot*line6Gray: gray50\\
&gnuplot*line7Gray: gray70\\
&gnuplot*line8Gray: gray30\\
\hline
\end{tabular}
\end{center}

\subsubsubsection{Line{\tt\_}resources}
{\bf gnuplot} honors the following resources for setting the width (in pixels) of
plot lines (shown here with their default values.)  0 or 1 means a minimal
width line of 1 pixel width.  A value of 2 or 3 may improve the appearance of
some plots.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*borderWidth: 2\\
&gnuplot*axisWidth: 0\\
&gnuplot*line1Width: 0\\
&gnuplot*line2Width: 0\\
&gnuplot*line3Width: 0\\
&gnuplot*line4Width: 0\\
&gnuplot*line5Width: 0\\
&gnuplot*line6Width: 0\\
&gnuplot*line7Width: 0\\
&gnuplot*line8Width: 0\\
\hline
\end{tabular}
\end{center}

{\bf gnuplot} honors the following resources for setting the dash style used for
plotting lines.  0 means a solid line.  A two-digit number {\bf jk} ({\bf j} and {\bf k}
are $>$= 1  and $<$= 9) means a dashed line with a repeated pattern of {\bf j} pixels
on followed by {\bf k} pixels off.  For example, '16' is a {\tt"}dotted{\tt"} line with one
pixel on followed by six pixels off.  More elaborate on/off patterns can be
specified with a four-digit value.  For example, '4441' is four on, four off,
four on, one off.  The default values shown below are for monochrome displays
or monochrome rendering on color or grayscale displays.  For color displays,
the default for each is 0 (solid line) except for {\bf axisDashes} which defaults
to a '16' dotted line.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*borderDashes: 0\\
&gnuplot*axisDashes: 16\\
&gnuplot*line1Dashes: 0\\
&gnuplot*line2Dashes: 42\\
&gnuplot*line3Dashes: 13\\
&gnuplot*line4Dashes: 44\\
&gnuplot*line5Dashes: 15\\
&gnuplot*line6Dashes: 4441\\
&gnuplot*line7Dashes: 42\\
&gnuplot*line8Dashes: 13\\
\hline
\end{tabular}
\end{center}
\subsubsection{Cgi}
The {\bf cgi} and {\bf hcgi} terminal drivers support SCO CGI drivers.  {\bf hcgi} is for
printers; the environment variable CGIPRNT must be set.  {\bf cgi} may be used
for either a display or hardcopy; if the environment variable CGIDISP is set,
then that display is used.  Otherwise CGIPRNT is used.

These terminals have no options.
\subsubsection{Cgm}
The {\bf cgm} terminal generates a Computer Graphics Metafile.  This file format
is a subset of the ANSI X3.122-1986 standard entitled {\tt"}Computer Graphics -
Metafile for the Storage and Transfer of Picture Description Information{\tt"}.
Several options may be set in {\bf cgm}.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal cgm {<mode>} {<color>} {<rotation>} {solid | dashed}
                      {width <plot_width>} {linewidth <line_width>}
                      {"<font>"} {<fontsize>}
\end{verbatim}
\postverbatim

where $<$mode$>$ is {\bf landscape}, {\bf portrait}, or {\bf default};
$<$color$>$ is either {\bf color} or {\bf monochrome}; 
$<$rotation$>$ is either {\bf rotate} or {\bf norotate};
{\bf solid} draws all curves with solid lines, overriding any dashed patterns;
$<$plot{\tt\_}width$>$ is the width of the page in points; 
$<$line{\tt\_}width$>$ is the line width in points; 
$<$font$>$ is the name of a font; and 
{\bf $<$fontsize$>$} is the size of the font in points.

By default, {\bf cgm} uses rotated text for the Y axis label.

The first six options can be in any order.  Selecting {\bf default} sets all
options to their default values.

Examples:
\preverbatim
\begin{verbatim}
     set terminal cgm landscape color rotate dashed width 432 \
                    linewidth 1  'Arial Bold' 12       # defaults
     set terminal cgm 14 linewidth 2  14  # wider lines & larger font
     set terminal cgm portrait 'Times Roman Italic' 12
     set terminal cgm color solid    # no pesky dashes!
\end{verbatim}
\postverbatim
\subsubsubsection{Font}
The first part of a Computer Graphics Metafile, the metafile description,
includes a font table.  In the picture body, a font is designated by an
index into this table.  By default, this terminal generates a table with
the following fonts:

\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{2}{|c|}{CGM fonts}\\
&Arial&\\
&Arial Italic&\\
&Arial Bold&\\
&Arial Bold Italic&\\
&Times Roman&\\
&Times Roman Italic&\\
&Times Roman Bold&\\
&Times Roman Bold Italic&\\
&Helvetica&\\
&Roman&\\
\hline
\end{tabular}
\end{center}
Case is not distinct, but the modifiers must appear in the above order (that
is, not 'Arial Italic Bold').  'Arial Bold' is the default font.

You may also specify a font name which does not appear in the default font
table.  In that case, a new font table is constructed with the specified
font as its only entry.  You must ensure that the spelling, capitalization,
and spacing of the name are appropriate for the application that will read
the CGM file.
\subsubsubsection{Fontsize}
Fonts are scaled assuming the page is 6 inches wide.  If the {\bf size} command
is used to change the aspect ratio of the page or the CGM file is converted
to a different width (e.g. it is imported into a document in which the
margins are not 6 inches apart), the resulting font sizes will be different.
To change the assumed width, use the {\bf width} option.
\subsubsubsection{Linewidth}
The {\bf linewidth} option sets the width of lines in pt.  The default width is
1 pt.  Scaling is affected by the actual width of the page, as discussed
under the {\bf fontsize} and {\bf width} options
\subsubsubsection{Rotate}
The {\bf norotate} option may be used to disable text rotation.  For example,
the CGM input filter for Word for Windows 6.0c can accept rotated text, but
the DRAW editor within Word cannot.  If you edit a graph (for example, to
label a curve), all rotated text is restored to horizontal.  The Y axis
label will then extend beyond the clip boundary.  With {\bf norotate}, the Y
axis label starts in a less attractive location, but the page can be edited
without damage.  The {\bf rotate} option confirms the default behavior.
\subsubsubsection{Solid}
The {\bf solid} option may be used to disable dashed line styles in the
plots.  This is useful when color is enabled and the dashing of the lines
detracts from the appearance of the plot. The {\bf dashed} option confirms the
default behavior, which gives a different dash pattern to each curve.
\subsubsubsection{Size}
Default size of a CGM page is 32599 units wide and 23457 units high for
landscape, or 23457 units wide by 32599 units high for portrait.
\subsubsubsection{Width}
All distances in the CGM file are in abstract units.  The application that
reads the file determines the size of the final page.  By default, the width
of the final page is assumed to be 6 inches (15.24 cm).  This distance is
used to calculate the correct font size, and may be changed with the {\bf width}
option.  The keyword should be followed by the width in points.  (Here, a
point is 1/72 inch, as in PostScript.  This unit is known as a {\tt"}big point{\tt"}
in TeX.)  {\bf gnuplot} arithmetic can be used to convert from other units, as
follows:
\preverbatim
\begin{verbatim}
     set terminal cgm width 432            # default
     set terminal cgm width 6*72           # same as above
     set terminal cgm width 10/2.54*72     # 10 cm wide
\end{verbatim}
\postverbatim
\subsubsubsection{Winword6}
The default font table was chosen to match, where possible, the default font
assignments made by the Computer Graphics Metafile input filter for
Microsoft Word 6.0c, although the filter makes available only 'Arial' and
'Times Roman' fonts and their bold and/or italic variants.  Other fonts such
as 'Helvetica' and 'Roman' are not available.  If the CGM file includes a
font table, the filter mostly ignores it.  However, it changes certain font
assignments so that they disagree with the table.  As a workaround, the
{\bf winword6} option deletes the font table from the CGM file.  In this case,
the filter makes predictable font assignments.  'Arial Bold' is correctly
assigned even with the font table present, which is one reason it was chosen
as the default.

{\bf winword6} disables the color tables for a similar reason --- with the color
table included, Microsoft Word displays black for color 7.

Linewidths and pointsizes may be changed with {\bf set linestyle}.
\subsubsection{Corel}
The {\bf corel} terminal driver supports CorelDraw.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal corel {  default
                         | {monochrome | color
                              {<fontname> {"<fontsize>" 
                                 {<xsize> <ysize> {<linewidth> }}}}}
\end{verbatim}
\postverbatim

where the fontsize and linewidth are specified in points and the sizes in
inches.  The defaults are monochrome, {\tt"}SwitzerlandLight{\tt"}, 22, 8.2, 10 and 1.2.
\subsubsection{Debug}
This terminal is provided to allow for the debugging of {\bf gnuplot}.  It is
likely to be of use only for users who are modifying the source code.
\subsubsection{Svga}
The {\bf svga} terminal driver supports PCs with SVGA graphics.  It can only be
be used if it is compiled with DJGPP.  Its only option is the font.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal svga {"<fontname>"}
\end{verbatim}
\postverbatim
\subsubsection{Dumb}
The {\bf dumb} terminal driver has an optional size specification and trailing
linefeed control.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal dumb {[no]feed} {<xsize> <ysize>}
\end{verbatim}
\postverbatim

where $<$xsize$>$ and $<$ysize$>$ set the size of the dumb terminals. Default is
79 by 24. The last newline is printed only if {\bf feed} is enabled.

Examples:
\preverbatim
\begin{verbatim}
     set term dumb nofeed
     set term dumb 79 49 # VGA screen---why would anyone do that?
\end{verbatim}
\postverbatim
\subsubsection{Dxf}
The {\bf dxf} terminal driver creates pictures that can be imported into AutoCad
(Release 10.x).  It has no options of its own, but some features of its plots
may be modified by other means.  The default size is 120x80 AutoCad units,
which can be changed by {\bf set size}.  {\bf dxf} uses seven colors (white, red,
yellow, green, cyan, blue and magenta), which can be changed only by
modifying the source file.  If a black-and-white plotting device is used, the
colors are mapped to differing line thicknesses.  See the description of the
AutoCad print/plot command.
\subsubsection{Dxy800a}
This terminal driver supports the Roland DXY800A plotter.  It has no options.
\subsubsection{Eepic}
The {\bf eepic} terminal driver supports the extended LaTeX picture environment.
It is an alternative to the {\bf latex} driver.

The output of this terminal is intended for use with the {\tt"}eepic.sty{\tt"} macro
package for LaTeX.  To use it, you need {\tt"}eepic.sty{\tt"}, {\tt"}epic.sty{\tt"} and a
printer driver that supports the {\tt"}tpic{\tt"} $\backslash$specials.  If your printer driver
doesn't support those $\backslash$specials, {\tt"}eepicemu.sty{\tt"} will enable you to use some
of them.

Although dotted and dashed lines are possible with {\bf eepic} and are tempting,
they do not work well for high-sample-rate curves, fusing the dashes all
together into a solid line.  For now, the {\bf eepic} driver creates only solid
lines.  There is another gnuplot driver ({\bf tpic}) that supports dashed lines,
but it cannot be used if your DVI driver doesn't support {\tt"}tpic{\tt"} $\backslash$specials.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '\{', you also need to include a '\}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX.  ---  If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']\{', the text itself, and finally, '\}'. The text itself may be anything
LaTeX can typeset as an LR-box. $\backslash$rule\{\}\{\}'s may help for best positioning.

The {\bf eepic} terminal has no options.

Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
\preverbatim
\begin{verbatim}
      set title '\LaTeX\ -- $ \gamma $'
\end{verbatim}
\postverbatim
Force centering both horizontally and vertically:
\preverbatim
\begin{verbatim}
      set label '{\LaTeX\ -- $ \gamma $}' at 0,0
\end{verbatim}
\postverbatim
Specify own positioning (top here):
\preverbatim
\begin{verbatim}
      set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
\end{verbatim}
\postverbatim
The other label -- account for long ticlabels:
\preverbatim
\begin{verbatim}
      set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
\end{verbatim}
\postverbatim
\subsubsection{Emxvga}
The {\bf emxvga}, {\bf emxvesa} and {\bf vgal} terminal drivers support PCs with SVGA,
vesa SVGA and VGA graphics boards, respectively.  They are intended to be
compiled with {\tt"}emx-gcc{\tt"} under either DOS or OS/2.  They also need VESA and
SVGAKIT maintained by Johannes Martin (JMARTIN@GOOFY.ZDV.UNI-MAINZ.DE) with
additions by David J. Liu (liu@phri.nyu.edu).

Syntax:
\preverbatim
\begin{verbatim}
     set terminal emxvga
     set terminal emxvesa {vesa-mode}
     set terminal vgal
\end{verbatim}
\postverbatim

The only option is the vesa mode for {\bf emxvesa}, which defaults to G640x480x256.
\subsubsection{Epson-180dpi}
This driver supports a family of Epson printers and derivatives.

{\bf epson-180dpi} and {\bf epson-60dpi} are drivers for Epson LQ-style 24-pin
printers with resolutions of 180 and 60 dots per inch, respectively.

{\bf epson-lx800} is a generic 9-pin driver appropriate for printers like the
Epson LX-800, the Star NL-10 and NX-1000, the PROPRINTER, and so forth.

{\bf nec-cp6} is generix 24-pin driver that can be used for printers like the
NEC CP6 and the Epson LQ-800.

The {\bf okidata} driver supports the 9-pin OKIDATA 320/321 Standard printers.

The {\bf starc} driver is for the Star Color Printer.

The {\bf tandy-60dpi} driver is for the Tandy DMP-130 series of 9-pin, 60-dpi
printers.

Only {\bf nec-cp6} has any options.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal nec-cp6 {monochrome | colour | draft}
\end{verbatim}
\postverbatim

which defaults to monochrome.

With each of these drivers, a binary copy is required on a PC to print.  Do
not use {\bf print} --- use instead {\bf copy file /b lpt1:}.
\subsubsection{Excl}
The {\bf excl} terminal driver supports Talaris printers such as the EXCL Laser
printer and the 1590.  It has no options.
\subsubsection{Hercules}
These drivers supports PC monitors with autodetected graphics boards.  They
can be used only when compiled with Zortech C/C++.  None have options.
\subsubsection{Fig}
The {\bf fig} terminal device generates output in the Fig graphics language.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal fig {monochrome | color} {small | big}
                      {pointsmax <max_points>}
                      {landscape | portrait}
                      {metric | inches}
                      {fontsize <fsize>}
                      {size <xsize> <ysize>}
                      {thickness <units>}
                      {depth <layer>}
\end{verbatim}
\postverbatim

{\bf monochrome} and {\bf color} determine whether the picture is black-and-white or
{\bf color}.  {\bf small} and {\bf big} produce a 5x3 or 8x5 inch graph in the default
{\bf landscape} mode and 3x5 or 5x8 inches in {\bf portrait} mode.  $<$max{\tt\_}points$>$
sets the maximum number of points per polyline.  Default units for editing
with {\tt"}xfig{\tt"} may be {\bf metric} or {\bf inches}.  {\bf fontsize} sets the size of the
text font to $<$fsize$>$ points.  {\bf size} sets (overrides) the size of the drawing
area to $<$xsize$>$*$<$ysize$>$ in units of inches or centimeters depending on the
{\bf inches} or {\bf metric} setting in effect.  {\bf depth} sets the default depth layer
for all lines and text.  The default depth is 10 to leave room for adding
material with {\tt"}xfig{\tt"} on top of the plot.

{\bf thickness} sets the default line thickness, which is 1 if not specified.
Overriding the thickness can be achieved by adding a multiple of 100 to the
to the {\bf linetype} value for a {\bf plot} command.  In a similar way the {\bf depth}
of plot elements (with respect to the default depth) can be controlled by
adding a multiple of 1000 to $<$linetype$>$.  The depth is then $<$layer$>$ +
$<$linetype$>$/1000 and the thickness is ($<$linetype$>$\%1000)/100 or, if that is
zero, the default line thickness.

Additional point-plot symbols are also available with the {\bf fig} driver. The
symbols can be used through {\bf pointtype} values \% 100 above 50, with different
fill intensities controlled by $<$pointtype$>$ \% 5 and outlines in black (for
$<$pointtype$>$ \% 10 $<$ 5) or in the current color.  Available symbols are
\preverbatim
\begin{verbatim}
       50 - 59:  circles
       60 - 69:  squares
       70 - 79:  diamonds
       80 - 89:  upwards triangles
       90 - 99:  downwards triangles
\end{verbatim}
\postverbatim
The size of these symbols is linked to the font size.  The depth of symbols
is by default one less than the depth for lines to achieve nice error bars.
If $<$pointtype$>$ is above 1000, the depth is $<$layer$>$ + $<$pointtype$>$/1000-1.  If
$<$pointtype$>$\%1000 is above 100, the fill color is ($<$pointtype$>$\%1000)/100-1.

Available fill colors are (from 1 to 9): black, blue, green, cyan, red,
magenta, yellow, white and dark blue (in monochrome mode: black for 1 to 6
and white for 7 to 9).

See {\bf plot with} for details of $<$linetype$>$ and $<$pointtype$>$.

The {\bf big} option is a substitute for the {\bf bfig} terminal in earlier versions,
which is no longer supported.

Examples:
\preverbatim
\begin{verbatim}
     set terminal fig monochrome small pointsmax 1000  # defaults
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     plot 'file.dat' with points linetype 102 pointtype 759
\end{verbatim}
\postverbatim
would produce circles with a blue outline of width 1 and yellow fill color.

\preverbatim
\begin{verbatim}
     plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 554
\end{verbatim}
\postverbatim
would produce errorbars with black lines and circles filled red.  These
circles are one layer above the lines (at depth 9 by default).

To plot the error bars on top of the circles use
\preverbatim
\begin{verbatim}
     plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 2554
\end{verbatim}
\postverbatim
\subsubsection{Gif}
The {\bf gif} terminal driver generates output in GIF format.  It uses Thomas
Boutell's gd library, which is available from http://www.boutell.com/gd/

By default, the {\bf gif} terminal driver uses a shared Web-friendy palette.
Syntax:
\preverbatim
\begin{verbatim}
     set terminal gif {transparent} {interlace}
                      {tiny | small | medium | large | giant}
                      {size <x>,<y>}
                      {<color0> <color1> <color2> ...}
\end{verbatim}
\postverbatim

{\bf transparent} instructs the driver to generate transparent GIFs.  The first
color will be the transparent one.

{\bf interlace} instructs the driver to generate interlaced GIFs.

The choice of fonts is {\bf tiny} (5x8 pixels), {\bf small} (6x12 pixels), {\bf medium}
(7x13 Bold), {\bf large} (8x16) or {\bf giant} (9x15 pixels)

The size $<$x,y$>$ is given in pixels --- it defaults to 640x480.  The number of
pixels can be also modified by scaling with the {\bf set size} command.

Each color must be of the form 'xrrggbb', where x is the literal character
'x' and 'rrggbb' are the red, green and blue components in hex.  For example,
'x00ff00' is green.  The background color is set first, then the border
colors, then the X \& Y axis colors, then the plotting colors.  The maximum
number of colors that can be set is 256.

Examples:
\preverbatim
\begin{verbatim}
     set terminal gif small size 640,480 \
                      xffffff x000000 x404040 \
                      xff0000 xffa500 x66cdaa xcdb5cd \
                      xadd8e6 x0000ff xdda0dd x9500d3    # defaults
\end{verbatim}
\postverbatim

which uses white for the non-transparent background, black for borders, gray
for the axes, and red, orange, medium aquamarine, thistle 3, light blue, blue,
plum and dark violet for eight plotting colors.

\preverbatim
\begin{verbatim}
     set terminal gif transparent xffffff \
                      x000000 x202020 x404040 x606060 \
                      x808080 xA0A0A0 xC0C0C0 xE0E0E0 \
\end{verbatim}
\postverbatim
which uses white for the transparent background, black for borders, dark
gray for axes, and a gray-scale for the six plotting colors.

The page size is 640x480 pixels.  The {\bf gif} driver can create either color
or monochromatic output, but you have no control over which is produced.

The current version of the {\bf gif} driver does not support animated GIFs.
\subsubsection{Unixplot}
The {\bf unixplot} driver produces device-independent output in the GNU plot
graphics language.  The default size of the PostScript results generated by
{\tt"}plot2ps{\tt"} is 5 x 3 inches; this can be increased up to about 8.25 x 8.25 by
{\bf set size}.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal unixplot {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

which defaults to 10-point {\tt"}Courier{\tt"}.

There is a non-GNU version of the {\bf unixplot} driver which cannot be compiled
unless this version is left out.
\subsubsection{Gpic}
The {\bf gpic} terminal driver generates GPIC graphs in the Free Software
Foundations's {\tt"}groff{\tt"} package.  The default size is 5 x 3 inches.  The only
option is the origin, which defaults to (0,0).

Syntax:
\preverbatim
\begin{verbatim}
     set terminal gpic {<x> <y>}
\end{verbatim}
\postverbatim

where {\bf x} and {\bf y} are in inches.

A simple graph can be formatted using

\preverbatim
\begin{verbatim}
     groff -p -mpic -Tps file.pic > file.ps.
\end{verbatim}
\postverbatim

The output from pic can be pipe-lined into eqn, so it is possible to put
complex functions in a graph with the {\bf set label} and {\bf set \{x/y\}label}
commands.  For instance,

\preverbatim
\begin{verbatim}
     set ylab '@space 0 int from 0 to x alpha ( t ) roman d t@'
\end{verbatim}
\postverbatim

will label the y axis with a nice integral if formatted with the command:

\preverbatim
\begin{verbatim}
     gpic filename.pic | geqn -d@@ -Tps | groff -m[macro-package] -Tps
         > filename.ps
\end{verbatim}
\postverbatim

Figures made this way can be scaled to fit into a document.  The pic language
is easy to understand, so the graphs can be edited by hand if need be.  All
co-ordinates in the pic-file produced by {\bf gnuplot} are given as x+gnuplotx
and y+gnuploty.  By default x and y are given the value 0.  If this line is
removed with an editor in a number of files, one can put several graphs in
one figure like this (default size is 5.0x3.0 inches):

\preverbatim
\begin{verbatim}
     .PS 8.0
     x=0;y=3
     copy "figa.pic"
     x=5;y=3
     copy "figb.pic"
     x=0;y=0
     copy "figc.pic"
     x=5;y=0
     copy "figd.pic"
     .PE
\end{verbatim}
\postverbatim

This will produce an 8-inch-wide figure with four graphs in two rows on top
of each other.

One can also achieve the same thing by the command

\preverbatim
\begin{verbatim}
     set terminal gpic x y
\end{verbatim}
\postverbatim

for example, using

\preverbatim
\begin{verbatim}
     .PS 6.0
     copy "trig.pic"
     .PE
\end{verbatim}
\postverbatim
\subsubsection{Gpr}
The {\bf gpr} terminal driver supports the Apollo Graphics Primitive Resource
for a fixed-size window.  It has no options.

If a variable window size is desired, use the {\bf apollo} terminal instead.
\subsubsection{Grass}
The {\bf grass} terminal driver gives {\bf gnuplot} capabilities to users of the 
GRASS geographic information system.  Contact grassp-list@moon.cecer.army.mil
for more information.  Pages are written to the current frame of the GRASS
Graphics Window.  There are no options.
\subsubsection{Hp2623a}
The {\bf hp2623a} terminal driver supports the Hewlett Packard HP2623A.  It has
no options.
\subsubsection{Hp2648}
The {\bf hp2648} terminal driver supports the Hewlett Packard HP2647 and HP2648.
It has no options.
\subsubsection{Hp500c}
The {\bf hp500c} terminal driver supports the Hewlett Packard HP DeskJet 500c.
It has options for resolution and compression.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal hp500c {<res>} {<comp>}
\end{verbatim}
\postverbatim

where {\bf res} can be 75, 100, 150 or 300 dots per inch and {\bf comp} can be {\tt"}rle{\tt"},
or {\tt"}tiff{\tt"}.  Any other inputs are replaced by the defaults, which are 75 dpi
and no compression.  Rasterization at the higher resolutions may require a
large amount of memory.
\subsubsection{Hpgl}
The {\bf hpgl} driver produces HPGL output for devices like the HP7475A plotter.
There are two options which can be set --- the number of pens and {\tt"}eject{\tt"}, which
tells the plotter to eject a page when done.  The default is to use 6 pens
and not to eject the page when done.

The international character sets ISO-8859-1 and CP850 are recognized via
{\bf set encoding iso{\tt\_}8859{\tt\_}1} or {\bf set encoding cp850} (see {\bf set encoding} for
details).

Syntax:
\preverbatim
\begin{verbatim}
     set terminal hpgl {<number_of_pens>} {eject}
\end{verbatim}
\postverbatim

The selection

\preverbatim
\begin{verbatim}
     set terminal hpgl 8 eject
\end{verbatim}
\postverbatim

is equivalent to the previous {\bf hp7550} terminal, and the selection

\preverbatim
\begin{verbatim}
     set terminal hpgl 4
\end{verbatim}
\postverbatim

is equivalent to the previous {\bf hp7580b} terminal.

The {\bf pcl5} driver supports the Hewlett-Packard Laserjet III.  It actually uses
HPGL-2, but there is a name conflict among the terminal devices.  It has
several options

Syntax:
\preverbatim
\begin{verbatim}
     set terminal pcl5 {<mode>} {<font>} {<fontsize>}
\end{verbatim}
\postverbatim

where $<$mode$>$ is {\bf landscape}, or {\bf portrait}, $<$font$>$ is {\bf stick}, {\bf univers}, or
{\bf cg{\tt\_}times}, and $<$fontsize$>$ is the size in points.

With {\bf pcl5} international characters are handled by the printer; you just put
the appropriate 8-bit character codes into the text strings.  You don't need
to bother with {\bf set encoding}.

HPGL graphics can be imported by many software packages.
\subsubsection{Hpljii}
The {\bf hpljii} terminal driver supports the HP Laserjet Series II printer.  The
{\bf hpdj} driver supports the HP DeskJet 500 printer.  These drivers allow a
choice of resolutions.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal hpljii | hpdj {<res>}
\end{verbatim}
\postverbatim

where {\bf res} may be 75, 100, 150 or 300 dots per inch; the default is 75.
Rasterization at the higher resolutions may require a large amount of memory.

The {\bf hp500c} terminal is similar to {\bf hpdj}; {\bf hp500c} additionally supports
color and compression.
\subsubsection{Hppj}
The {\bf hppj} terminal driver supports the HP PaintJet and HP3630 printers.  The
only option is the choice of font.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal hppj {FNT5X9 | FNT9X17 | FNT13X25}
\end{verbatim}
\postverbatim

with the middle-sized font (FNT9X17) being the default.
\subsubsection{Imagen}
The {\bf imagen} terminal driver supports Imagen laser printers.  It is capable
of placing multiple graphs on a single page.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal imagen {<fontsize>} {portrait | landscape}
                         {[<horiz>,<vert>]}
\end{verbatim}
\postverbatim

where {\bf fontsize} defaults to 12 points and the layout defaults to {\bf landscape}.
{\bf $<$horiz$>$} and {\bf $<$vert$>$} are the number of graphs in the horizontal and
vertical directions; these default to unity.

Example:
\preverbatim
\begin{verbatim}
     set terminal imagen portrait [2,3]
\end{verbatim}
\postverbatim

puts six graphs on the page in three rows of two in portrait orientation.
\subsubsection{Iris4d}
The {\bf iris4d} terminal driver supports Silicon Graphics IRIS 4D computers.
Its only option is 8- or 24-bit color depth.  The default is 8.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal iris4d {8 | 24}
\end{verbatim}
\postverbatim

The color depth is not really a choice -- the value appropriate for the
hardware should be selected.

When using 24-bit mode, the colors can be directly specified via the file
.gnuplot{\tt\_}iris4d that is searched in the current directory and then in the
home directory specified by the HOME environment variable.  This file holds
RGB values for the background, border, labels and nine plotting colors, in
that order.  For example, here is a file containing the default colors:

\preverbatim
\begin{verbatim}
     85   85   85     Background   (dark gray)
     0    0    0      Boundary     (black)
     170  0    170    Labeling     (magenta)
     85   255  255    Plot Color 1 (light cyan)
     170  0    0      Plot Color 2 (red)
     0    170  0      Plot Color 3 (green)
     255  85   255    Plot Color 4 (light magenta)
     255  255  85     Plot Color 5 (yellow)
     255  85   85     Plot Color 6 (light red)
     85   255  85     Plot Color 7 (light green)
     0    170  170    Plot Color 8 (cyan)
     170  170  0      Plot Color 9 (brown)
\end{verbatim}
\postverbatim

This file must have exactly 12 lines of RGB triples.  No empty lines are
allowed, and anything after the third number on a line is ignored.
\subsubsection{Kyo}
The {\bf kyo} and {\bf prescribe} terminal drivers support the Kyocera laser printer.
The only difference between the two is that {\bf kyo} uses {\tt"}Helvetica{\tt"} whereas
{\bf prescribe} uses {\tt"}Courier{\tt"}.  There are no options.
\subsubsection{Latex}
The {\bf latex} and {\bf emtex} drivers allow two options.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal latex | emtex {courier | roman | default} {<fontsize>}
\end{verbatim}
\postverbatim

{\bf fontsize} may be any size you specify.  The default is for the plot to
inherit its font setting from the embedding document.

Unless your driver is capable of building fonts at any size (e.g. dvips),
stick to the standard 10, 11 and 12 point sizes.

METAFONT users beware: METAFONT does not like odd sizes.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '\{', you also need to include a '\}' at the
end of the text, and the whole text will be centered both horizontally and
vertically.  If the text string begins with '[', you need to follow this with
a position specification (up to two out of t,b,l,r), ']\{', the text itself,
and finally '\}'.  The text itself may be anything LaTeX can typeset as an
LR-box.  '$\backslash$rule\{\}\{\}'s may help for best positioning.

Points, among other things, are drawn using the LaTeX commands {\tt"}$\backslash$Diamond{\tt"} and
{\tt"}$\backslash$Box{\tt"}.  These commands no longer belong to the LaTeX2e core; they are included
in the latexsym package, which is part of the base distribution and thus part
of any LaTeX implementation.  Please do not forget to use this package.

Points are drawn with the LaTex commands $\backslash$Diamond and $\backslash$Box.  These
commands do no longer belong to the LaTeX2e core, but are included in the
latexsym-package in the base distribution, and are hence part of all LaTeX
implementations. Please do not forget to use this package.

Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
\preverbatim
\begin{verbatim}
      set title '\LaTeX\ -- $ \gamma $'
\end{verbatim}
\postverbatim
Force centering both horizontally and vertically:
\preverbatim
\begin{verbatim}
      set label '{\LaTeX\ -- $ \gamma $}' at 0,0
\end{verbatim}
\postverbatim
Specify own positioning (top here):
\preverbatim
\begin{verbatim}
      set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
\end{verbatim}
\postverbatim
The other label -- account for long ticlabels:
\preverbatim
\begin{verbatim}
      set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
\end{verbatim}
\postverbatim
\subsubsection{Linux}
The {\bf linux} driver has no additional options to specify.  It looks at the
environment variable GSVGAMODE for the default mode; if not set, it uses
1024x768x256 as default mode or, if that is not possible, 640x480x16
(standard VGA).
\subsubsection{Macintosh}
Several options may be set in the 'macintosh' driver.

Syntax:
\preverbatim
\begin{verbatim}
    set terminal macintosh {singlewin | multiwin} {vertical | novertical}
                           {size <width>, <height> | default}
\end{verbatim}
\postverbatim

'singlewin' limits the output to a single window and is useful for animations.
'multiwin' allows multiple windows.
'vertical' is only valid under the gx option. With this option, rotated text
\preverbatim
\begin{verbatim}
   be drawn vertically. novertical turns this option off.
size <width>, <height> overrides the graph size set in the preferences
   dialog until it is cleared with either 'set term mac size default'
   or 'set term mac default'.
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
'set term mac size default' sets the window size settings to those set in
   the preferences dialog.
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
'set term mac default' sets all options to their default values.
   Default values: nogx, multiwin, novertical.
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
If you generate graphs under the multiwin option and then switch to singlewin,
the next plot command will cause one more window to be created. This new
window will be reused as long as singlewin is in effect. If you switch back
to multiwin, generate some graphs, and then switch to singlewin again, the
orginal 'singlewin' window will be resused if it is still open. Otherwise
a new 'singlewin' window will be created. The 'singlewin' window is not numbered.
\end{verbatim}
\postverbatim
\subsubsection{Mf}
The {\bf mf} terminal driver creates a input file to the METAFONT program.  Thus a
figure may be used in the TeX document in the same way as is a character.

To use a picture in a document, the METAFONT program must be run with the
output file from {\bf gnuplot} as input.  Thus, the user needs a basic knowledge
of the font creating process and the procedure for including a new font in a
document.  However, if the METAFONT program is set up properly at the local
site, an unexperienced user could perform the operation without much trouble.

The text support is based on a METAFONT character set.  Currently the
Computer Modern Roman font set is input, but the user is in principal free to
chose whatever fonts he or she needs.  The METAFONT source files for the
chosen font must be available.  Each character is stored in a separate
picture variable in METAFONT.  These variables may be manipulated (rotated,
scaled etc.) when characters are needed.  The drawback is the interpretation
time in the METAFONT program.  On some machines (i.e. PC) the limited amount
of memory available may also cause problems if too many pictures are stored.

The {\bf mf} terminal has no options.
\subsubsubsection{METAFONT Instructions}

- Set your terminal to METAFONT:
\preverbatim
\begin{verbatim}
 set terminal mf
\end{verbatim}
\postverbatim
- Select an output-file, e.g.:
\preverbatim
\begin{verbatim}
 set output "myfigures.mf"
\end{verbatim}
\postverbatim
- Create your pictures. Each picture will generate a separate character. Its
default size will be 5*3 inches. You can change the size by saying {\bf set size
0.5,0.5} or whatever fraction of the default size you want to have.

- Quit {\bf gnuplot}.

- Generate a TFM and GF file by running METAFONT on the output of {\bf gnuplot}.
Since the picture is quite large (5*3 in), you will have to use a version of
METAFONT that has a value of at least 150000 for memmax.  On Unix systems
these are conventionally installed under the name bigmf.  For the following
assume that the command virmf stands for a big version of METAFONT.  For
example:

- Invoke METAFONT:
\preverbatim
\begin{verbatim}
   virmf '&plain'
\end{verbatim}
\postverbatim
- Select the output device: At the METAFONT prompt ('*') type:
\preverbatim
\begin{verbatim}
   \mode:=CanonCX;     % or whatever printer you use
\end{verbatim}
\postverbatim
- Optionally select a magnification:
\preverbatim
\begin{verbatim}
   mag:=1;             % or whatever you wish
\end{verbatim}
\postverbatim
- Input the {\bf gnuplot}-file:
\preverbatim
\begin{verbatim}
   input myfigures.mf
\end{verbatim}
\postverbatim
On a typical Unix machine there will usually be a script called {\tt"}mf{\tt"} that
executes virmf '\&plain', so you probably can substitute mf for virmf \&plain.
This will generate two files: mfput.tfm and mfput.\$\$\$gf (where \$\$\$ indicates
the resolution of your device).  The above can be conveniently achieved by
typing everything on the command line, e.g.:
virmf '\&plain' '$\backslash$mode:=CanonCX; mag:=1; input myfigures.mf'
In this case the output files will be named myfigures.tfm and
myfigures.300gf.

- Generate a PK file from the GF file using gftopk:
\preverbatim
\begin{verbatim}
 gftopk myfigures.300gf myfigures.300pk
\end{verbatim}
\postverbatim
The name of the output file for gftopk depends on the DVI driver you use.
Ask your local TeX administrator about the naming conventions.  Next, either
install the TFM and PK files in the appropriate directories, or set your
environment variables properly.  Usually this involves setting TEXFONTS to
include the current directory and doing the same thing for the environment
variable that your DVI driver uses (no standard name here...).  This step is
necessary so that TeX will find the font metric file and your DVI driver will
find the PK file.

- To include your pictures in your document you have to tell TeX the font:
\preverbatim
\begin{verbatim}
 \font\gnufigs=myfigures
\end{verbatim}
\postverbatim
Each picture you made is stored in a single character.  The first picture is
character 0, the second is character 1, and so on...  After doing the above
step, you can use the pictures just like any other characters.  Therefore, to
place pictures 1 and 2 centered in your document, all you have to do is:
\preverbatim
\begin{verbatim}
 \centerline{\gnufigs\char0}
 \centerline{\gnufigs\char1}
\end{verbatim}
\postverbatim
in plain TeX.  For LaTeX you can, of course, use the picture environment and
place the picture wherever you wish by using the $\backslash$makebox and $\backslash$put macros.

This conversion saves you a lot of time once you have generated the font;
TeX handles the pictures as characters and uses minimal time to place them,
and the documents you make change more often than the pictures do.  It also
saves a lot of TeX memory.  One last advantage of using the METAFONT driver
is that the DVI file really remains device independent, because no $\backslash$special
commands are used as in the eepic and tpic drivers.
\subsubsection{Mp}

The {\bf mp} driver produces output intended to be input to the Metapost program.
Running Metapost on the file creates EPS files containing the plots. By
default, Metapost passes all text through TeX.  This has the advantage of
allowing essentially  any TeX symbols in titles and labels.

The {\bf mp} terminal is selected with a command of the form
\preverbatim
\begin{verbatim}
  set term mp {color} {solid} {notex} {mag <magsize>} {"<name>"} {<size>}
\end{verbatim}
\postverbatim
The option {\bf color} causes lines to be drawn in color (on a printer or display
that supports it), {\bf monochrome} (or nothing) selects black lines.  The option
{\bf solid} draws solid lines, while {\bf dashed} (or nothing) selects lines with
different patterns of dashes.  If {\bf solid} is selected but {\bf color} is not,
nearly all lines will be identical.  This may occasionally be useful, so it is
allowed.

The option {\bf notex} bypasses TeX entirely, therefore no TeX code can be used in
labels under this option.  This is intended for use on old plot files or files
that make frequent use of common characters like {\bf \$} and {\bf \%} that require
special handling in TeX.

Changing font sizes in TeX has no effect on the size of mathematics, and there
is no foolproof way to make such a change, except by globally  setting a
magnification factor. This is the purpose of the {\bf magnification} option. It
must be followed by a scaling factor. All text (NOT the graphs) will be scaled
by this factor. Use this if you have math that you want at some size other
than the default 10pt. Unfortunately, all math will be the same size, but see
the discussion below on editing the MP output. {\bf mag} will also work under
{\bf notex} but there seems no point in using it as the font size option (below)
works as well.

A name in quotes selects the font that will be used when no explicit font is
given in a {\bf set label} or {\bf set title}.  A name recognized by TeX (a TFM file
exists) must be used.  The default is {\tt"}cmr10{\tt"} unless {\bf notex} is selected,
then it is {\tt"}pcrr8r{\tt"} (Courier).  Even under {\bf notex}, a TFM file is needed by
Metapost. The file {\bf pcrr8r.tfm} is the name given to Courier in LaTeX's psnfss
package.  If you change the font from the {\bf notex} default, choose a font that
matches the ASCII encoding at least in the range 32-126.  {\bf cmtt10} almost
works, but it has a nonblank character in position 32 (space).

The size can be any number between 5.0 and 99.99.  If it is omitted, 10.0 is
used.  It is advisable to use {\bf magstep} sizes: 10 times an integer or
half-integer power of 1.2, rounded to two decimals, because those are the most
available sizes of fonts in TeX systems.

All the options are optional.  If font information is given, it must be at the
end, with size (if present) last.  The size is needed to select a size for the
font, even if the font name includes size information.  For example,
{\bf set term mp {\tt"}cmtt12{\tt"}} selects cmtt12 shrunk to the default size 10.  This
is probably not what you want or you would have used cmtt10.

The following common ascii characters need special treatment in TeX:
\preverbatim
\begin{verbatim}
  $, &, #, %, _;  |, <, >;  ^, ~,  \, {, and }
\end{verbatim}
\postverbatim
The five characters \$, \#, \&, {\tt\_}, and \% can simply be escaped, e.g., {\bf $\backslash$\$}.
The three characters $<$, $>$, and $|$ can be wrapped in math mode, e.g., {\bf \$$<$\$}.
The remainder require some TeX work-arounds.  Any good book on TeX will give
some guidance.

If you type your labels inside double quotes, backslashes in TeX code need to
be escaped (doubled). Using single quotes will avoid having to do this, but
then you cannot use {\bf $\backslash$n} for line breaks.  As of this writing, version 3.7 of
gnuplot processess titles given in a {\bf plot} command differently than in other
places, and backslashes in TeX commands need to be doubled regardless of the
style of quotes.

Metapost pictures are typically used in TeX documents.  Metapost deals with
fonts pretty much the same way TeX does, which is different from most other
document preparation programs.  If the picture is included in a LaTeX document
using the graphics package, or in a plainTeX document via epsf.tex, and then
converted to PostScript with dvips (or other dvi-to-ps converter), the text in
the plot will usually be handled correctly.  However, the text may not appear
if you send the Metapost output as-is to a PostScript interpreter.

\subsubsubsection{Metapost Instructions}

- Set your terminal to Metapost, e.g.:
\preverbatim
\begin{verbatim}
  set terminal mp mono "cmtt12" 12
\end{verbatim}
\postverbatim

- Select an output-file, e.g.:
\preverbatim
\begin{verbatim}
  set output "figure.mp"
\end{verbatim}
\postverbatim

- Create your pictures.  Each plot (or multiplot group) will generate a
separate Metapost beginfig...endfig group.  Its default size will be 5 by 3
inches.  You can change the size by saying {\bf set size 0.5,0.5} or whatever
fraction of the default size you want to have.

- Quit gnuplot.

- Generate EPS files by running Metapost on the output of gnuplot:
\preverbatim
\begin{verbatim}
  mpost figure.mp  OR  mp figure.mp
\end{verbatim}
\postverbatim
The name of the Metapost program depends on the system, typically {\bf mpost} for
a Unix machine and {\bf mp} on many others.  Metapost will generate one EPS file
for each picture.

- To include your pictures in your document you can use the graphics package
in LaTeX or epsf.tex in plainTeX:
\preverbatim
\begin{verbatim}
  \usepackage{graphics} % LaTeX
  \input epsf.tex       % plainTeX
\end{verbatim}
\postverbatim
If you use a driver other than dvips for converting TeX DVI output to PS, you
may need to add the following line in your LaTeX document:
\preverbatim
\begin{verbatim}
  \DeclareGraphicsRule{*}{eps}{*}{}
\end{verbatim}
\postverbatim
Each picture you made is in a separate file.  The first picture is in, e.g.,
figure.0, the second in figure.1, and so on....  To place the third picture in
your document, for example, all you have to do is:
\preverbatim
\begin{verbatim}
  \includegraphics{figure.2} % LaTeX
  \epsfbox{figure.2}         % plainTeX
\end{verbatim}
\postverbatim

The advantage, if any, of the mp terminal over a postscript terminal is
editable output.  Considerable effort went into making this output as clean as
possible.  For those knowledgeable in the Metapost language, the default line
types and colors can be changed by editing the arrays {\bf lt[]} and {\bf col[]}.
The choice of solid vs dashed lines, and color vs black lines can be change by
changing the values assigned to the booleans {\bf dashedlines} and {\bf colorlines}.
If the default {\bf tex} option was in effect, global changes to the text of
labels can be achieved by editing the {\bf vebatimtex...etex} block.  In
particular, a LaTeX preamble can be added if desired, and then LaTeX's
built-in size changing commands can be used for maximum flexibility. Be sure
to set the appropriate MP configuration variable to force Metapost to run
LaTeX instead of plainTeX.
\subsubsection{Mgr}
The {\bf mgr} terminal driver supports the Mgr Window system.  It has no options.
\subsubsection{Mif}
The {\bf mif} terminal driver produces Frame Maker MIF format version 3.00.  It
plots in MIF Frames with the size 15*10 cm, and plot primitives with the same
pen will be grouped in the same MIF group.  Plot primitives in a {\bf gnuplot}
page will be plotted in a MIF Frame, and several MIF Frames are collected in
one large MIF Frame.  The MIF font used for text is {\tt"}Times{\tt"}.

Several options may be set in the MIF 3.00 driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal mif {colour | monochrome} {polyline | vectors}
                      {help | ?}
\end{verbatim}
\postverbatim

{\bf colour} plots lines with line types $>$= 0 in colour (MIF sep. 2--7) and
{\bf monochrome} plots all line types in black (MIF sep. 0).
{\bf polyline} plots curves as continuous curves and {\bf vectors} plots curves as
collections of vectors.
{\bf help} and {\bf ?} print online help on standard error output --- both print a
short description of the usage; {\bf help} also lists the options;

Examples:
\preverbatim
\begin{verbatim}
     set term mif colour polylines    # defaults
     set term mif                     # defaults
     set term mif vectors
     set term mif help
\end{verbatim}
\postverbatim
\subsubsection{Mtos}
The {\bf mtos} terminal has no options.  It sends data via a pipe to an external
program called GPCLIENT.  It runs under MULTITOS, Magic 3.x, MagicMAC. and
MiNT.  If you cannot find GPCLIENT, than mail to dirk@lstm.uni-erlangen.de.
\subsubsection{Next}
Several options may be set in the next driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal next {<mode>} {<type> } {<color>} {<dashed>}
                {"<fontname>"} {<fontsize>} title {"<newtitle>"}
\end{verbatim}
\postverbatim

where $<$mode$>$ is  {\bf default}, which sets all options to their defaults;
$<$type$>$ is either {\bf new} or {\bf old}, where {\bf old} invokes the old single window;
$<$color$>$ is either {\bf color} or {\bf monochrome};
$<$dashed$>$ is either {\bf solid} or {\bf dashed};
{\tt"}$<$fontname$>${\tt"} is the name of a valid PostScript font;
$<$fontsize$>$ is the size of the font in PostScript points; and
$<$title$>$ is the title for the GnuTerm window.
Defaults are  {\bf new}, {\bf monochrome}, {\bf dashed}, {\tt"}Helvetica{\tt"}, 14pt.

Examples:
\preverbatim
\begin{verbatim}
     set term next default
     set term next 22
     set term next color "Times-Roman" 14
     set term next color "Helvetica" 12 title "MyPlot"
     set term next old
\end{verbatim}
\postverbatim

Pointsizes may be changed with {\bf set linestyle}.
\subsubsection{Next}
Several options may be set in the next driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal next {<mode>} {<type> } {<color>} {<dashed>}
                {"<fontname>"} {<fontsize>} title {"<newtitle>"}
\end{verbatim}
\postverbatim

where $<$mode$>$ is  {\bf default}, which sets all options to their defaults;
$<$type$>$ is either {\bf new} or {\bf old}, where {\bf old} invokes the old single window;
$<$color$>$ is either {\bf color} or {\bf monochrome};
$<$dashed$>$ is either {\bf solid} or {\bf dashed};
{\tt"}$<$fontname$>${\tt"} is the name of a valid PostScript font;
$<$fontsize$>$ is the size of the font in PostScript points; and
$<$title$>$ is the title for the GnuTerm window.
Defaults are  {\bf new}, {\bf monochrome}, {\bf dashed}, {\tt"}Helvetica{\tt"}, 14pt.

Examples:
\preverbatim
\begin{verbatim}
     set term next default
     set term next 22
     set term next color "Times-Roman" 14
     set term next color "Helvetica" 12 title "MyPlot"
     set term next old
\end{verbatim}
\postverbatim

Pointsizes may be changed with {\bf set linestyle}.
\subsubsection{Pbm}
Several options may be set in the {\bf pbm} terminal --- the driver for PBMplus.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal pbm {<fontsize>} {<mode>}
\end{verbatim}
\postverbatim

where $<$fontsize$>$ is {\bf small}, {\bf medium}, or {\bf large} and $<$mode$>$ is {\bf monochrome},
{\bf gray} or {\bf color}.  The default plot size is 640 pixels wide and 480 pixels
high; this may be changed by {\bf set size}.

The output of the {\bf pbm} driver depends upon $<$mode$>$: {\bf monochrome} produces a
portable bitmap (one bit per pixel), {\bf gray} a portable graymap (three bits
per pixel) and {\bf color} a portable pixmap (color, four bits per pixel).

The output of this driver can be used with Jef Poskanzer's excellent PBMPLUS
package, which provides programs to convert the above PBMPLUS formats to GIF,
TIFF, MacPaint, Macintosh PICT, PCX, X11 bitmap and many others.  PBMPLUS may
be obtained from ftp.x.org.  The relevant files have names that begin with
{\tt"}netpbm-1mar1994.p1{\tt"}; they reside in /contrib/utilities.  The package can
probably also be obtained from one of the many sites that mirrors ftp.x.org.

Examples:
\preverbatim
\begin{verbatim}
     set terminal pbm small monochrome             # defaults
     set size 2,2; set terminal pbm color medium
\end{verbatim}
\postverbatim
\subsubsection{Dospc}
The {\bf dospc} terminal driver supports PCs with arbitrary graphics boards, which
will be automatically detected.  It should be used only if you are not using
the gcc or Zortec C/C++ compilers.
\subsubsection{Pm}
The {\bf pm} terminal driver provides an OS/2 Presentation Manager window in
which the graph is plotted.  The window is opened when the first graph is
plotted.  This window has its own online help as well as facilities for
printing, copying to the clipboard and some line type and color adjustments.
The {\bf multiplot} option is supported.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal pm {server {n}} {persist} {widelines} {enhanced} {"title"}
\end{verbatim}
\postverbatim

If {\bf persist} is specified, each graph appears in its own window and all
windows remain open after {\bf gnuplot} exits.  If {\bf server} is specified, all
graphs appear in the same window, which remains open when {\bf gnuplot} exits.
This option takes an optional numerical argument which specifies an instance
of the server process.  Thus multiple server windows can be in use at the
same time.

If {\bf widelines} is specified, all plots will be drawn with wide lines.  If
{\bf enhanced} is specified, sub- and superscripts and multiple fonts are
enabled using the same syntax as the {\bf enhanced postscript} option (see
{\bf set terminal postscript enhanced} for details).  Font names for the basic
PostScript fonts may be abbreviated to single letters.

If {\bf title} is specified, it will be used as the title of the plot window.
It will also be used as the name of the server instance, and will override
the optional numerical argument.

Linewidths may be changed with {\bf set linestyle}.
\subsubsection{Png}
The {\bf png} terminal driver supports Portable Network Graphics.  To compile it,
you will need  the third-party libraries {\tt"}libpng{\tt"} and {\tt"}zlib{\tt"}; both are
available at ftp://ftp.uu.net/graphics/png.  {\bf png} has two options.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal png {small | medium | large}
                      {monochrome | gray | color}
\end{verbatim}
\postverbatim

The defaults are small (fontsize) and monochrome.  Default size of the output
is 640*480 pixel.
\subsubsection{Postscript}
Several options may be set in the {\bf postscript} driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal postscript {<mode>} {enhanced | noenhanced}
                             {color | monochrome} {solid | dashed}
                             {<duplexing>}
                             {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

where $<$mode$>$ is {\bf landscape}, {\bf portrait}, {\bf eps} or {\bf default};
{\bf solid} draws all plots with solid lines, overriding any dashed patterns;
$<$duplexing$>$ is {\bf defaultplex}, {\bf simplex} or {\bf duplex} ({\tt"}duplexing{\tt"} in
PostScript is the ability of the printer to print on both sides of the same
page --- don't set this if your printer can't do it);
{\bf enhanced} activates the {\tt"}enhanced PostScript{\tt"} features (subscripts,
superscripts and mixed fonts);
{\bf {\tt"}$<$fontname$>${\tt"}} is the name of a valid PostScript font; and {\bf $<$fontsize$>$} is
the size of the font in PostScript points.

{\bf default} mode sets all options to their defaults: {\bf landscape}, {\bf monochrome},
{\bf dashed}, {\bf defaultplex}, {\bf noenhanced}, {\tt"}Helvetica{\tt"} and 14pt.
\preverbatim
\begin{verbatim}
Default size of a PostScript plot is 10 inches wide and 7 inches high.
\end{verbatim}
\postverbatim

{\bf eps} mode generates EPS (Encapsulated PostScript) output, which is just
regular PostScript with some additional lines that allow the file to be
imported into a variety of other applications.  (The added lines are
PostScript comment lines, so the file may still be printed by itself.)  To
get EPS output, use the {\bf eps} mode and make only one plot per file.  In {\bf eps}
mode the whole plot, including the fonts, is reduced to half of the default
size.

Examples:
\preverbatim
\begin{verbatim}
     set terminal postscript default       # old postscript
     set terminal postscript enhanced      # old enhpost
     set terminal postscript landscape 22  # old psbig
     set terminal postscript eps 14        # old epsf1
     set terminal postscript eps 22        # old epsf2
     set size 0.7,1.4; set term post portrait color "Times-Roman" 14
\end{verbatim}
\postverbatim

Linewidths and pointsizes may be changed with {\bf set linestyle}.

The {\bf postscript} driver supports about 70 distinct pointtypes, selectable
through the {\bf pointtype} option on {\bf plot} and {\bf set linestyle}.

Several possibly useful files about {\bf gnuplot}'s PostScript are included
in the /docs/ps subdirectory of the {\bf gnuplot} distribution and at the
distribution sites.  These are {\tt"}ps{\tt\_}symbols.gpi{\tt"} (a {\bf gnuplot} command file
that, when executed, creates the file {\tt"}ps{\tt\_}symbols.ps{\tt"} which shows all the
symbols available through the {\bf postscript} terminal), {\tt"}ps{\tt\_}guide.ps{\tt"} (a
PostScript file that contains a summary of the enhanced syntax and a page
showing what the octal codes produce with text and symbol fonts) and
{\tt"}ps{\tt\_}file.doc{\tt"} (a text file that contains a discussion of the organization
of a PostScript file written by {\bf gnuplot}).

A PostScript file is editable, so once {\bf gnuplot} has created one, you are
free to modify it to your heart's desire.  See the {\tt"}editing postscript{\tt"}
section for some hints.
\subsubsubsection{Enhanced postscript}

\begin{center}
\begin{tabular}{|ccl|} \hline
\multicolumn{3}{|c|}{Enhanced Text Control Codes} \\ \hline
Control & Examples & Explanation \\ \hline
\verb~^~ & \verb~a^x~ & superscript\\
\verb~_~ & \verb~a_x~ & subscript\\
\verb~@~ & \verb~@x or a@^b_c~ & phantom box (occupies no width)\\
\verb~&~ & \verb~&{space}~ & inserts space of specified length\\
\hline
\end{tabular}
\end{center}

Braces can be used to place multiple-character text where a single character
is expected (e.g., 2\verb+^+\{10\}).  To change the font and/or size, use the full
form:  \{/[fontname][=fontsize $|$ *fontscale] text\}.  Thus \{/Symbol=20 G\} is a
20-point GAMMA) and \{/*0.75 K\} is a K at three-quarters of whatever fontsize
is currently in effect.  (The '/' character MUST be the first character after
the '\{'.)

If the encoding vector has been changed by {\bf set encoding}, the default
encoding vector can be used instead by following the slash with a dash.  This
is unnecessary if you use the Symbol font, however --- since /Symbol uses its
own encoding vector, {\bf gnuplot} will not apply any other encoding vector to
it.

The phantom box is useful for a@\verb+^+b{\tt\_}c to align superscripts and subscripts
but does not work well for overwriting an accent on a letter.  (To do the
latter, it is much better to use {\bf set encoding iso{\tt\_}8859{\tt\_}1} to change to the
ISO Latin-1 encoding vector, which contains a large variety of letters with
accents or other diacritical marks.)  Since the box is non-spacing, it is
sensible to put the shorter of the subscript or superscript in the box (that
is, after the @).

Space equal in length to a string can be inserted using the '\&' character.
Thus
\preverbatim
\begin{verbatim}
       'abc&{def}ghi'
\end{verbatim}
\postverbatim
would produce
\preverbatim
\begin{verbatim}
       'abc   ghi'.
\end{verbatim}
\postverbatim

You can access special symbols numerically by specifying $\backslash$character-code (in
octal), e.g., \{/Symbol $\backslash$245\} is the symbol for infinity.

You can escape control characters using $\backslash$, e.g.,  $\backslash$$\backslash$, $\backslash$\{, and so on.

But be aware that strings in double-quotes are parsed differently than those
enclosed in single-quotes.  The major difference is that backslashes may need
to be doubled when in double-quoted strings.

Examples (these are hard to describe in words --- try them!):
\preverbatim
\begin{verbatim}
     set xlabel 'Time (10^6 {/Symbol m}s)'
     set title '{/Symbol=18 \362@_{/=9.6 0}^{/=12 x}} \
                {/Helvetica e^{-{/Symbol m}^2/2} d}{/Symbol m}'
\end{verbatim}
\postverbatim

The file {\tt"}ps{\tt\_}guide.ps{\tt"} in the /docs/ps subdirectory of the {\bf gnuplot} source
distribution contains more examples of the enhanced syntax.
\subsubsubsection{Editing postscript}
The PostScript language is a very complex language --- far too complex to
describe in any detail in this document.  Nevertheless there are some things
in a PostScript file written by {\bf gnuplot} that can be changed without risk of
introducing fatal errors into the file.

For example, the PostScript statement {\tt"}/Color true def{\tt"} (written into the
file in response to the command {\bf set terminal postscript color}), may be
altered in an obvious way to generate a black-and-white version of a plot.
Similarly line colors, text colors, line weights and symbol sizes can also be
altered in straight-forward ways.  Text (titles and labels) can be edited to
correct misspellings or to change fonts.  Anything can be repositioned, and
of course anything can be added or deleted, but modifications such as these
may require deeper knowledge of the PostScript language.

The organization of a PostScript file written by {\bf gnuplot} is discussed in
the text file {\tt"}ps{\tt\_}file.doc{\tt"} in the /docs/ps subdirectory.
\subsubsection{Pslatex and pstex}
The {\bf pslatex} and {\bf pstex} drivers generate output for further processing by
LaTeX and TeX, respectively.  Figures generated by {\bf pstex} can be included
in any plain-based format (including LaTeX).

Syntax:
\preverbatim
\begin{verbatim}
     set terminal pslatex | |pstex {<color>} {<dashed>} {<rotate>}
                                   {auxfile} {<font_size>}
\end{verbatim}
\postverbatim

$<$color$>$ is either {\bf color} or {\bf monochrome}.  $<$rotate$>$ is either {\bf rotate} or
{\bf norotate} and determines if the y-axis label is rotated.  $<$font{\tt\_}size$>$ is
used to scale the font from its usual size.

If {\bf auxfile} is specified, it directs the driver to put the PostScript
commands into an auxiliary file instead of directly into the LaTeX file.
This is useful if your pictures are large enough that dvips cannot handle
them.  The name of the auxiliary PostScript file is derived from the name of
the TeX file given on the {\bf set output} command; it is determined by replacing
the trailing {\bf .tex} (actually just the final extent in the file name) with
{\bf .ps} in the output file name, or, if the TeX file has no extension, {\bf .ps}
is appended.  Remember to close the file before leaving {\bf gnuplot}.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '\{', you also need to include a '\}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX.  ---  If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']\{', the text itself, and finally, '\}'. The text itself may be anything
LaTeX can typeset as an LR-box. $\backslash$rule\{\}\{\}'s may help for best positioning.

Examples:
\preverbatim
\begin{verbatim}
     set term pslatex monochrome dashed rotate       # set to defaults
\end{verbatim}
\postverbatim
To write the PostScript commands into the file {\tt"}foo.ps{\tt"}:
\preverbatim
\begin{verbatim}
     set term pslatex auxfile
     set output "foo.tex"; plot ...: set output
\end{verbatim}
\postverbatim
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
\preverbatim
\begin{verbatim}
      set title '\LaTeX\ -- $ \gamma $'
\end{verbatim}
\postverbatim
Force centering both horizontally and vertically:
\preverbatim
\begin{verbatim}
      set label '{\LaTeX\ -- $ \gamma $}' at 0,0
\end{verbatim}
\postverbatim
Specify own positioning (top here):
\preverbatim
\begin{verbatim}
      set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
\end{verbatim}
\postverbatim
The other label -- account for long ticlabels:
\preverbatim
\begin{verbatim}
      set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
\end{verbatim}
\postverbatim

Linewidths and pointsizes may be changed with {\bf set linestyle}.
\subsubsection{Pstricks}
The {\bf pstricks} driver is intended for use with the {\tt"}pstricks.sty{\tt"} macro
package for LaTeX.  It is an alternative to the {\bf eepic} and {\bf latex} drivers.
You need {\tt"}pstricks.sty{\tt"}, and, of course, a printer that understands
PostScript, or a converter such as Ghostscript.

PSTricks is available via anonymous ftp from the /pub directory at
Princeton.EDU.  This driver definitely does not come close to using the full
capability of the PSTricks package.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal pstricks {hacktext | nohacktext} {unit | nounit}
\end{verbatim}
\postverbatim

The first option invokes an ugly hack that gives nicer numbers; the second
has to do with plot scaling.  The defaults are {\bf hacktext} and {\bf nounit}.
\subsubsection{Qms}
The {\bf qms} terminal driver supports the QMS/QUIC Laser printer, the Talaris
1200 and others.  It has no options.
\subsubsection{Regis}
The {\bf regis} terminal device generates output in the REGIS graphics language.
It has the option of using 4 (the default) or 16 colors.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal regis {4 | 16}
\end{verbatim}
\postverbatim
\subsubsection{Rgip}
The {\bf rgip} and {\bf uniplex} terminal drivers support RGIP metafiles.  They can
combine several graphs on a single page, but only one page is allowed in a
given output file.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal rgip | uniplex {portrait | landscape}
                                 {[<horiz>,<vert>]} {<fontsize>}
\end{verbatim}
\postverbatim

permissible values for the font size are in the range 1--8, with the default
being 1.  The default layout is landscape.  Graphs are placed on the page in
a {\bf horiz}x{\bf vert} grid, which defaults to [1,1].

Example:
\preverbatim
\begin{verbatim}
     set terminal uniplex portrait [2,3]
\end{verbatim}
\postverbatim

puts six graphs on a page in three rows of two in portrait orientation.
\subsubsection{Sun}
The {\bf sun} terminal driver supports the SunView window system.  It has no
options.
\subsubsection{Tek410x}
The {\bf tek410x} terminal driver supports the 410x and 420x family of Tektronix
terminals.  It has no options.
\subsubsection{Table}
Instead of producing a graph, the {\bf table} terminal prints out the points on
which a graph would be based, i.e., the results of processing the {\bf plot} or
{\bf splot} command, in a multicolumn ASCII table of X Y \{Z\} R values.  The
character R takes on one of three values: {\tt"}i{\tt"} if the point is in the active
range, {\tt"}o{\tt"} if it is out-of-range, or {\tt"}u{\tt"} if it is undefined.  The data
format is determined by the format of the axis labels (see {\bf set format}).

For those times when you want the numbers, you can display them on the
screen or save them to a file.  This can be useful if you want to generate
contours and then save them for further use, perhaps for plotting with
{\bf plot};  see {\bf set contour} for an example.  The same method can be used to
save interpolated data (see {\bf set samples} and {\bf set dgrid3d}).
\subsubsection{Tek40}
This family of terminal drivers supports a variety of VT-like terminals.
{\bf tek40xx} supports Tektronix 4010 and others as well as most TEK emulators;
{\bf vttek} supports VT-like tek40xx terminal emulators; {\bf kc-tek40xx} supports
MS-DOS Kermit Tek4010 terminal emulators in color: {\bf km-tek40xx} supports them
in monochrome; {\bf selanar} supports Selanar graphics; and {\bf bitgraph} supports
BBN Bitgraph terminals.  None have any options.
\subsubsection{Texdraw}
The {\bf texdraw} terminal driver supports the LaTeX texdraw environment.  It is
intended for use with {\tt"}texdraw.sty{\tt"} and {\tt"}texdraw.tex{\tt"} in the texdraw package.

It has no options.
\subsubsection{Tgif}
Tgif is an X11-based drawing tool --- it has nothing to do with GIF.

The {\bf tgif} driver supports different pointsizes (with {\bf set pointsize}),
different label fonts and font sizes (e.g. {\bf set label {\tt"}Hallo{\tt"} at x,y font
{\tt"}Helvetica,34{\tt"}}) and multiple graphs on the page.  The proportions of the
axes are not changed.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal tgif {portrait | landscape} {<[x,y]>}
                       {solid | dashed}
                       {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

where $<$[x,y]$>$ specifies the number of graphs in the x and y directions on the
page, {\tt"}$<$fontname$>${\tt"} is the name of a valid PostScript font, and $<$fontsize$>$
specifies the size of the PostScript font.  Defaults are {\bf portrait}, {\bf [1,1]},
{\bf dashed}, {\bf {\tt"}Helvetica{\tt"}}, and {\bf 18}.

The {\bf solid} option is usually prefered if lines are colored, as they often
are in the editor.  Hardcopy will be black-and-white, so {\bf dashed} should be
chosen for that.

Multiplot is implemented in two different ways.

The first multiplot implementation is the standard gnuplot multiplot feature:

\preverbatim
\begin{verbatim}
     set terminal tgif
     set output "file.obj"
     set multiplot
     set origin x01,y01
     set size  xs,ys
     plot ...
          ...
     set origin x02,y02
     plot ...
     set nomultiplot
\end{verbatim}
\postverbatim

See {\bf set multiplot} for further information.

The second version is the [x,y] option for the driver itself.  The advantage
of this implementation is that everything is scaled and placed automatically
without the need for setting origins and sizes; the graphs keep their natural
x/y proportions of 3/2 (or whatever is fixed by {\bf set size}).

If both multiplot methods are selected, the standard method is chosen and a
warning message is given.

Examples of single plots (or standard multiplot):
\preverbatim
\begin{verbatim}
     set terminal tgif                  # defaults
     set terminal tgif "Times-Roman" 24
     set terminal tgif landscape
     set terminal tgif landscape solid
\end{verbatim}
\postverbatim

Examples using the built-in multiplot mechanism:
\preverbatim
\begin{verbatim}
     set terminal tgif portrait [2,4]  # portrait; 2 plots in the x-
                                       # and 4 in the y-direction
     set terminal tgif [1,2]           # portrait; 1 plot in the x-
                                       # and 2 in the y-direction
     set terminal tgif landscape [3,3] # landscape; 3 plots in both
                                       # directions
\end{verbatim}
\postverbatim
\subsubsection{Tkcanvas}
This terminal driver generates Tk canvas widget commands based on Tcl/Tk
(default) or Perl.  To use it, rebuild {\bf gnuplot} (after uncommenting or
inserting the appropriate line in {\tt"}term.h{\tt"}), then

\preverbatim
\begin{verbatim}
gnuplot> set term tkcanvas {perltk} {interactive}
gnuplot> set output 'plot.file'
\end{verbatim}
\postverbatim

After invoking {\tt"}wish{\tt"}, execute the following sequence of Tcl/Tk commands:

\preverbatim
\begin{verbatim}
% source plot.file
% canvas .c
% pack .c
% gnuplot .c
\end{verbatim}
\postverbatim

Or, for Perl/Tk use a program like this:

\preverbatim
\begin{verbatim}
use Tk;
my $top = MainWindow->new;
my $c = $top->Canvas;
$c->pack();
do "plot.pl";
gnuplot->($c);
MainLoop;
\end{verbatim}
\postverbatim

The code generated by {\bf gnuplot} creates a procedure called {\tt"}gnuplot{\tt"}
that takes the name of a canvas as its argument.  When the procedure is
called, it clears the canvas, finds the size of the canvas and draws the plot
in it, scaled to fit.

For 2-dimensional plotting ({\bf plot}) two additional procedures are defined:
{\tt"}gnuplot{\tt\_}plotarea{\tt"} will return a list containing the borders of the plotting
area {\tt"}xleft, xright, ytop, ybot{\tt"} in canvas screen coordinates, while the ranges
of the two axes {\tt"}x1min, x1max, y1min, y1max, x2min, x2max, y2min, y2max{\tt"} in plot
coordinates can be obtained calling {\tt"}gnuplot{\tt\_}axisranges{\tt"}.
If the {\tt"}interactive{\tt"} option is specified, mouse clicking on a line segment
will print the coordinates of its midpoint to stdout. Advanced actions
can happen instead if the user supplies a procedure named
{\tt"}user{\tt\_}gnuplot{\tt\_}coordinates{\tt"}, which takes the following arguments:
{\tt"}win id x1s y1s x2s y2s x1e y1e x2e y2e x1m y1m x2m y2m{\tt"},
the name of the canvas and the id of the line segment followed by the
coordinates of its start and end point in the two possible axis ranges; the
coordinates of the midpoint are only filled for logarithmic axes.

The current version of {\bf tkcanvas} supports neither {\bf multiplot} nor {\bf replot}.
\subsubsection{Tpic}
The {\bf tpic} terminal driver supports the LaTeX picture environment with tpic
$\backslash$specials.  It is an alternative to the {\bf latex} and {\bf eepic} terminal drivers.
Options are the point size, line width, and dot-dash interval.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal tpic <pointsize> <linewidth> <interval>
\end{verbatim}
\postverbatim

where {\bf pointsize} and {\bf linewidth} are integers in milli-inches and {\bf interval}
is a float in inches.  If a non-positive value is specified, the default is
chosen: pointsize = 40, linewidth = 6, interval = 0.1.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '\{', you also need to include a '\}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX.  ---  If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']\{', the text itself, and finally, '\}'. The text itself may be anything
LaTeX can typeset as an LR-box. $\backslash$rule\{\}\{\}'s may help for best positioning.

Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
\preverbatim
\begin{verbatim}
      set title '\LaTeX\ -- $ \gamma $'
\end{verbatim}
\postverbatim
Force centering both horizontally and vertically:
\preverbatim
\begin{verbatim}
      set label '{\LaTeX\ -- $ \gamma $}' at 0,0
\end{verbatim}
\postverbatim
Specify own positioning (top here):
\preverbatim
\begin{verbatim}
      set xlabel '[t]{\LaTeX\ -- $ \gamma $}'
\end{verbatim}
\postverbatim
The other label -- account for long ticlabels:
\preverbatim
\begin{verbatim}
      set ylabel '[r]{\LaTeX\ -- $ \gamma $\rule{7mm}{0pt}'
\end{verbatim}
\postverbatim
\subsubsection{Unixpc}
The {\bf unixpc} terminal driver supports AT\&T 3b1 and AT\&T 7300 Unix PC.  It has
no options.
\subsubsection{Unixplot}
The {\bf unixplot} terminal driver generates output in the Unix {\tt"}plot{\tt"} graphics
language.  It has no options.

This terminal cannot be compiled if the GNU version of plot is to be used;
in that case, use the {\bf gnugraph} terminal instead.
\subsubsection{Vx384}
The {\bf vx384} terminal driver supports the Vectrix 384 and Tandy color
printers.  It has no options.
\subsubsection{VWS}
The {\bf VWS} terminal driver supports the VAX Windowing System.  It has
no options.  It will sense the display type (monochrome, gray scale,
or color.)  All line styles are plotted as solid lines.
\subsubsection{Windows}
Three options may be set in the {\bf windows} terminal driver.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal windows {<color>} {"<fontname>"} {<fontsize>}
\end{verbatim}
\postverbatim

where {\bf $<$color$>$} is either {\bf color} or {\bf monochrome}, {\bf {\tt"}$<$fontname$>${\tt"}} is the
name of a valid Windows font, and {\bf $<$fontsize$>$} is the size of the font in
points.

Other options may be set with the graph-menu, the initialization file,
and {\bf set linestyle}.

The Windows version normally terminates immediately as soon as the end of
any files given as command line arguments is reached (i.e. in non-interactive
mode). It will also not show the text-window at all, in this mode, only
the plot. By giving the optional argument
{\bf /noend} or {\bf -noend}, you can disable this behaviour.
\subsubsubsection{Graph-menu}
The {\bf gnuplot graph} window has the following options on a pop-up menu
accessed by pressing the right mouse button or selecting {\bf Options} from the
system menu:

{\bf Bring to Top} when checked brings the graph window to the top after every
plot.

{\bf Color} when checked enables color linestyles.  When unchecked it forces
monochrome linestyles.

{\bf Copy to Clipboard} copies a bitmap and a Metafile picture.

{\bf Background...} sets the window background color.

{\bf Choose Font...} selects the font used in the graphics window.

{\bf Line Styles...} allows customization of the line colors and styles.

{\bf Print...} prints the graphics windows using a Windows printer driver and
allows selection of the printer and scaling of the output.  The output
produced by {\bf Print} is not as good as that from {\bf gnuplot}'s own printer
drivers.

{\bf Update wgnuplot.ini} saves the current window locations, window sizes, text
window font, text window font size, graph window font, graph window font
size, background color and linestyles to the initialization file
{\bf WGNUPLOT.INI}.
\subsubsubsection{Printing}
In order of preference, graphs may be be printed in the following ways.

{\bf 1.} Use the {\bf gnuplot} command {\bf set terminal} to select a printer and {\bf set
output} to redirect output to a file.

{\bf 2.} Select the {\bf Print...} command from the {\bf gnuplot graph} window.  An extra
command {\bf screendump} does this from the text window.

{\bf 3.} If {\bf set output {\tt"}PRN{\tt"}} is used, output will go to a temporary file.  When
you exit from {\bf gnuplot} or when you change the output with another {\bf set
output} command, a dialog box will appear for you to select a printer port.
If you choose OK, the output will be printed on the selected port, passing
unmodified through the print manager.  It is possible to accidentally (or
deliberately) send printer output meant for one printer to an incompatible
printer.
\subsubsubsection{Text-menu}
The {\bf gnuplot text} window has the following options on a pop-up menu accessed
by pressing the right mouse button or selecting {\bf Options} from the system
menu:

{\bf Copy to Clipboard} copies marked text to the clipboard.

{\bf Paste} copies text from the clipboard as if typed by the user.

{\bf Choose Font...} selects the font used in the text window.

{\bf System Colors} when selected makes the text window honor the System Colors
set using the Control Panel.  When unselected, text is black or blue on a
white background.

{\bf Update wgnuplot.ini} saves the current text window location, text window
size, text window font and text window font size to the initialisation file
{\bf WGNUPLOT.INI}.

{\bf MENU BAR}

If the menu file {\bf WGNUPLOT.MNU} is found in the same directory as
WGNUPLOT.EXE, then the menu specified in {\bf WGNUPLOT.MNU} will be loaded.
Menu commands:

[Menu] starts a new menu with the name on the following line.

[EndMenu] ends the current menu.

[--] inserts a horizontal menu separator.

[$|$] inserts a vertical menu separator.

[Button] puts the next macro on a push button instead of a menu.

Macros take two lines with the macro name (menu entry) on the first line and
the macro on the second line.  Leading spaces are ignored.  Macro commands:

[INPUT]  ---  Input string with prompt terminated by [EOS] or \{ENTER\}

[EOS]  ---  End Of String terminator.  Generates no output.

[OPEN]  ---  Get name of file to open from list box, with title of list box
terminated by [EOS], followed by default filename terminated by [EOS] or
\{ENTER\}.  This uses COMMDLG.DLL from Windows 3.1.

[SAVE]  ---  Get name of file to save.  Similar to [OPEN]

Macro character substitutions:

\{ENTER\}  ---  Carriage Return '$\backslash$r'

\{TAB\}  ---  Tab '$\backslash$011'

\{ESC\}  ---  Escape '$\backslash$033'

\{\verb+^+A\}  ---  '$\backslash$001'

...

\{\verb+^+{\tt\_}\}  ---  '$\backslash$031'

Macros are limited to 256 characters after expansion.
\subsubsubsection{Wgnuplot.ini}
Windows {\bf gnuplot} will read some of its options from the {\bf [WGNUPLOT]} section
of {\bf WGNUPLOT.INI} in the Windows directory.  A sample {\bf WGNUPLOT.INI} file:

\preverbatim
\begin{verbatim}
     [WGNUPLOT]
     TextOrigin=0 0
     TextSize=640 150
     TextFont=Terminal,9
     GraphOrigin=0 150
     GraphSize=640 330
     GraphFont=Arial,10
     GraphColor=1
     GraphToTop=1
     GraphBackground=255 255 255
     Border=0 0 0 0 0
     Axis=192 192 192 2 2
     Line1=0 0 255 0 0
     Line2=0 255 0 0 1
     Line3=255 0 0 0 2
     Line4=255 0 255 0 3
     Line5=0 0 128 0 4
\end{verbatim}
\postverbatim

The {\bf GraphFont} entry specifies the font name and size in points.  The five
numbers given in the {\bf Border}, {\bf Axis} and {\bf Line} entries are the {\bf Red}
intensity (0--255), {\bf Green} intensity, {\bf Blue} intensity, {\bf Color Linestyle}
and {\bf Mono Linestyle}.  {\bf Linestyles} are 0=SOLID, 1=DASH, 2=DOT, 3=DASHDOT,
4=DASHDOTDOT.  In the sample {\bf WGNUPLOT.INI} file above, Line 2 is a green
solid line in color mode, or a dashed line in monochrome mode.  The default
line width is 1 pixel.  If {\bf Linestyle} is negative, it specifies the width of
a SOLID line in pixels.  Line1 and any linestyle used with the {\bf points} style
must be SOLID with unit width.
\subsubsubsection{Windows3.0}
Windows 3.1 is preferred, but WGNUPLOT will run under Windows 3.0 with the
following restrictions:
{\bf 1.} COMMDLG.DLL and SHELL.DLL (available with Windows 3.1 or Borland C++
3.1) must be in the windows directory.

{\bf 2.} WGNUPLOT.HLP produced by Borland C++ 3.1 is in Windows 3.1 format.
You need to use the WINHELP.EXE supplied with Borland C++ 3.1.

{\bf 3.} It will not run in real mode due to lack of memory.

{\bf 4.} TrueType fonts are not available in the graph window.

{\bf 5.} Drag-drop does not work.
\subsubsection{X11}
{\bf gnuplot} provides the {\bf x11} terminal type for use with X servers.  This
terminal type is set automatically at startup if the {\bf DISPLAY} environment
variable is set, if the {\bf TERM} environment variable is set to {\bf xterm}, or
if the {\bf -display} command line option is used.

Syntax:
\preverbatim
\begin{verbatim}
     set terminal x11 {reset} {<n>}
\end{verbatim}
\postverbatim

Multiple plot windows are supported: {\bf set terminal x11 $<$n$>$} directs the
output to plot window number n.  If n$>$0, the terminal number will be
appended to the window title and the icon will be labeled {\bf gplt $<$n$>$}.
The active window may distinguished by a change in cursor (from default
to crosshair.)

Plot windows remain open even when the {\bf gnuplot} driver is changed to a
different device.  A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing {\bf close} from a window
manager menu.  All plot windows can be closed by specifying {\bf reset}, which
actually terminates the subprocess which maintains the windows (unless
{\bf -persist} was specified).

Plot windows will automatically be closed at the end of the session
unless the {\bf -persist} option was given.

The size or aspect ratio of a plot may be changed by resizing the {\bf gnuplot}
window.

Linewidths and pointsizes may be changed from within {\bf gnuplot} with
{\bf set linestyle}.

For terminal type {\bf x11}, {\bf gnuplot} accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file.  See the X(1) man page
(or its equivalent) for a description of such options.

A number of other {\bf gnuplot} options are available for the {\bf x11} terminal.
These may be specified either as command-line options when {\bf gnuplot} is
invoked or as resources in the configuration file {\tt"}/.Xdefaults{\tt"}.  They are
set upon initialization and cannot be altered during a {\bf gnuplot} session.
\subsubsubsection{Command-line{\tt\_}options}
In addition to the X Toolkit options, the following options may be specified
on the command line when starting {\bf gnuplot} or as resources in your
{\tt"}.Xdefaults{\tt"} file:

\begin{center}
\begin{tabular}{|cl|} \hline
`-mono`  & forces monochrome rendering on color displays.\\
`-gray`  & requests grayscale rendering on grayscale or color displays.\\
         & (Grayscale displays receive monochrome rendering by default.) \\
`-clear` & requests that the window be cleared momentarily before a\\
         & new plot is displayed. \\
`-tvtwm` & requests that geometry specifications for position of the\\
         & window be made relative to the currently displayed portion\\
         & of the virtual root. \\
`-raise` & raise plot window after each plot. \\
`-noraise` & do not raise plot window after each plot. \\
`-persist`&plot windows survive after main gnuplot program exits. \\
\hline
\end{tabular}
\end{center}
The options are shown above in their command-line syntax.  When entered as
resources in {\tt"}.Xdefaults{\tt"}, they require a different syntax.

Example:
\preverbatim
\begin{verbatim}
     gnuplot*gray: on
\end{verbatim}
\postverbatim

{\bf gnuplot} also provides a command line option ({\bf -pointsize $<$v$>$}) and a
resource, {\bf gnuplot*pointsize: $<$v$>$}, to control the size of points plotted
with the {\bf points} plotting style.  The value {\bf v} is a real number (greater
than 0 and less than or equal to ten) used as a scaling factor for point
sizes.  For example, {\bf -pointsize 2} uses points twice the default size, and
{\bf -pointsize 0.5} uses points half the normal size.
\subsubsubsection{Monochome{\tt\_}options}
For monochrome displays, {\bf gnuplot} does not honor foreground or background
colors.  The default is black-on-white.  {\bf -rv} or {\bf gnuplot*reverseVideo: on}
requests white-on-black.

\subsubsubsection{Color{\tt\_}resources}
For color displays, {\bf gnuplot} honors the following resources (shown here
with their default values) or the greyscale resources.  The values may be
color names as listed in the X11 rgb.txt file on your system, hexadecimal
RGB color specifications (see X11 documentation), or a color name followed
by a comma and an {\bf intensity} value from 0 to 1.  For example, {\bf blue, 0.5}
means a half intensity blue.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*background: white\\
&gnuplot*textColor: black\\
&gnuplot*borderColor: black\\
&gnuplot*axisColor: black\\
&gnuplot*line1Color: red\\
&gnuplot*line2Color: green\\
&gnuplot*line3Color: blue\\
&gnuplot*line4Color: magenta\\
&gnuplot*line5Color: cyan\\
&gnuplot*line6Color: sienna\\
&gnuplot*line7Color: orange\\
&gnuplot*line8Color: coral\\
\hline
\end{tabular}
\end{center}

The command-line syntax for these is, for example,

Example:
\preverbatim
\begin{verbatim}
     gnuplot -background coral
\end{verbatim}
\postverbatim

\subsubsubsection{Grayscale{\tt\_}resources}
When {\bf -gray} is selected, {\bf gnuplot} honors the following resources for
grayscale or color displays (shown here with their default values).  Note
that the default background is black.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*background: black\\
&gnuplot*textGray: white\\
&gnuplot*borderGray: gray50\\
&gnuplot*axisGray: gray50\\
&gnuplot*line1Gray: gray100\\
&gnuplot*line2Gray: gray60\\
&gnuplot*line3Gray: gray80\\
&gnuplot*line4Gray: gray40\\
&gnuplot*line5Gray: gray90\\
&gnuplot*line6Gray: gray50\\
&gnuplot*line7Gray: gray70\\
&gnuplot*line8Gray: gray30\\
\hline
\end{tabular}
\end{center}

\subsubsubsection{Line{\tt\_}resources}
{\bf gnuplot} honors the following resources for setting the width (in pixels) of
plot lines (shown here with their default values.)  0 or 1 means a minimal
width line of 1 pixel width.  A value of 2 or 3 may improve the appearance of
some plots.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*borderWidth: 2\\
&gnuplot*axisWidth: 0\\
&gnuplot*line1Width: 0\\
&gnuplot*line2Width: 0\\
&gnuplot*line3Width: 0\\
&gnuplot*line4Width: 0\\
&gnuplot*line5Width: 0\\
&gnuplot*line6Width: 0\\
&gnuplot*line7Width: 0\\
&gnuplot*line8Width: 0\\
\hline
\end{tabular}
\end{center}

{\bf gnuplot} honors the following resources for setting the dash style used for
plotting lines.  0 means a solid line.  A two-digit number {\bf jk} ({\bf j} and {\bf k}
are $>$= 1  and $<$= 9) means a dashed line with a repeated pattern of {\bf j} pixels
on followed by {\bf k} pixels off.  For example, '16' is a {\tt"}dotted{\tt"} line with one
pixel on followed by six pixels off.  More elaborate on/off patterns can be
specified with a four-digit value.  For example, '4441' is four on, four off,
four on, one off.  The default values shown below are for monochrome displays
or monochrome rendering on color or grayscale displays.  For color displays,
the default for each is 0 (solid line) except for {\bf axisDashes} which defaults
to a '16' dotted line.

\begin{center}
\begin{tabular}{|cl|} \hline
&gnuplot*borderDashes: 0\\
&gnuplot*axisDashes: 16\\
&gnuplot*line1Dashes: 0\\
&gnuplot*line2Dashes: 42\\
&gnuplot*line3Dashes: 13\\
&gnuplot*line4Dashes: 44\\
&gnuplot*line5Dashes: 15\\
&gnuplot*line6Dashes: 4441\\
&gnuplot*line7Dashes: 42\\
&gnuplot*line8Dashes: 13\\
\hline
\end{tabular}
\end{center}
\subsubsection{Xlib}
The {\bf xlib} terminal driver supports the X11 Windows System.  It generates
gnulib{\tt\_}x11 commands.  {\bf set term x11} behaves similarly to {\bf set terminal xlib;
set output {\tt"}$|$gnuplot{\tt\_}x11{\tt"}}.  {\bf xlib} has no options, but see {\bf x11}.
\subsection{Tics}
The {\bf set tics} command can be used to change the tics to be drawn outwards.

Syntax:
\preverbatim
\begin{verbatim}
     set tics {<direction>}
     show tics
\end{verbatim}
\postverbatim

where $<$direction$>$ may be {\bf in} (the default) or {\bf out}.

See also {\bf set xtics} for more control of major (labelled) tic marks and {\bf set
mxtics} for control of minor tic marks.
\subsection{Ticslevel}
Using {\bf splot}, one can adjust the relative height of the vertical (Z) axis
using {\bf set ticslevel}.  The numeric argument provided specifies the location
of the bottom of the scale (as a fraction of the z-range) above the xy-plane.
The default value is 0.5.  Negative values are permitted, but tic labels on
the three axes may overlap.

To place the xy-plane at a position 'pos' on the z-axis, {\bf ticslevel} should
be set equal to  (pos - zmin) / (zmin - zmax).

Syntax:
\preverbatim
\begin{verbatim}
     set ticslevel {<level>}
     show tics
\end{verbatim}
\postverbatim

See also {\bf set view}.
\subsection{Ticscale}
The size of the tic marks can be adjusted with {\bf set ticscale}.

Syntax:
\preverbatim
\begin{verbatim}
     set ticscale {<major> {<minor>}}
     show tics
\end{verbatim}
\postverbatim

If $<$minor$>$ is not specified, it is 0.5*$<$major$>$.  The default size is 1.0 for
major tics and 0.5 for minor tics.  Note that it is possible to have the tic
marks pointing outward by specifying a negative size.
\subsection{Timestamp}
The command {\bf set timestamp} places the time and date of the plot in the left
margin.

Syntax:
\preverbatim
\begin{verbatim}
     set timestamp {"<format>"} {top|bottom} {{no}rotate}
                   {<xoff>}{,<yoff>} {"<font>"}
     set notimestamp
     show timestamp
\end{verbatim}
\postverbatim

The format string allows you to choose the format used to write the date and
time.  Its default value is what asctime() uses: {\tt"}\%a \%b \%d \%H:\%M:\%S \%Y{\tt"}
(weekday, month name, day of the month, hours, minutes, seconds, four-digit
year).  With {\bf top} or {\bf bottom} you can place the timestamp at the top or
bottom of the left margin (default: bottom).  {\bf rotate} lets you write the
timestamp vertically, if your terminal supports vertical text.  The constants
$<$xoff$>$ and $<$off$>$ are offsets from the default position given in character
screen coordinates.  $<$font$>$ is used to specify the font with which the time
is to be written.

The abbreviation {\bf time} may be used in place of {\bf timestamp}.

Example:
\preverbatim
\begin{verbatim}
     set timestamp "%d/%m/%y %H:%M" 80,-2 "Helvetica"
\end{verbatim}
\postverbatim

See {\bf set timefmt} for more information about time format strings.
\subsection{Timefmt}
This command applies to timeseries where data are composed of dates/times.
It has no meaning unless the command {\bf set xdata time} is given also.

Syntax:
\preverbatim
\begin{verbatim}
     set timefmt "<format string>"
     show timefmt
\end{verbatim}
\postverbatim

The string argument tells {\bf gnuplot} how to read timedata from the datafile.
The valid formats are:


\begin{center}
\begin{tabular}{|cl|} \hline
\multicolumn{2}{|c|}{Time Series timedata Format Specifiers}\\
\hline \hline
Format & Explanation \\ \hline
\verb@%d@ & day of the month, 1--31 \\
\verb@%m@ & month of the year, 1--12 \\
\verb@%y@ & year, 0--99 \\
\verb@%Y@ & year, 4-digit \\
\verb@%j@ & day of the year, 1--365 \\
\verb@%H@ & hour, 0--24 \\
\verb@%M@ & minute, 0--60 \\
\verb@%S@ & second, 0--60 \\
\verb@%b@ & three-character abbreviation of the name of the month \\
\verb@%B@ & name of the month \\
\hline
\end{tabular}
\end{center}
Any character is allowed in the string, but must match exactly.  $\backslash$t (tab) is
recognized.  Backslash-octals ($\backslash$nnn) are converted to char.  If there is no
separating character between the time/date elements, then \%d, \%m, \%y, \%H, \%M
and \%S read two digits each, \%Y reads four digits and \%j reads three digits.
\%b requires three characters, and \%B requires as many as it needs.

Spaces are treated slightly differently.  A space in the string stands for
zero or more whitespace characters in the file.  That is, {\tt"}\%H \%M{\tt"} can be used
to read {\tt"}1220{\tt"} and {\tt"}12     20{\tt"} as well as {\tt"}12 20{\tt"}.

Each set of non-blank characters in the timedata counts as one column in the
{\bf using n:n} specification.  Thus {\bf 11:11  25/12/76  21.0} consists of three
columns.  To avoid confusion, {\bf gnuplot} requires that you provide a complete
{\bf using} specification if your file contains timedata.

Since {\bf gnuplot} cannot read non-numerical text, if the date format includes
the day or month in words, the format string must exclude this text.  But
it can still be printed with the {\tt"}\%a{\tt"}, {\tt"}\%A{\tt"}, {\tt"}\%b{\tt"}, or {\tt"}\%B{\tt"} specifier: see
{\bf set format} for more details about these and other options for printing
timedata.  ({\bf gnuplot} will determine the proper month and weekday from the
numerical values.)

See also {\bf set xdata} and {\bf Time/date} for more information.

Example:
\preverbatim
\begin{verbatim}
     set timefmt "%d/%m/%Y\t%H:%M"
\end{verbatim}
\postverbatim
tells {\bf gnuplot} to read date and time separated by tab.  (But look closely at
your data --- what began as a tab may have been converted to spaces somewhere
along the line; the format string must match what is actually in the file.)
\subsection{Title}
The {\bf set title} command produces a plot title that is centered at the top of
the plot.  {\bf set title} is a special case of {\bf set label}.

Syntax:
\preverbatim
\begin{verbatim}
     set title {"<title-text>"} {<xoff>}{,<yoff>} {"<font>,{<size>}"}
     show title
\end{verbatim}
\postverbatim

Specifying constants $<$xoff$>$ or $<$yoff$>$ as optional offsets for the title will
move the title $<$xoff$>$ or $<$yoff$>$ character screen coordinates (not graph
coordinates).  For example, {\tt"}{\bf set title ,-1}{\tt"} will change only the y offset
of the title, moving the title down by roughly the height of one character.

$<$font$>$ is used to specify the font with which the title is to be written;
the units of the font $<$size$>$ depend upon which terminal is used.

{\bf set title} with no parameters clears the title.

See {\bf syntax} for details about the processing of backslash sequences and
the distinction between single- and double-quotes.
\subsection{Tmargin}
The command {\bf set tmargin} sets the size of the top margin.  Please see
{\bf set margin} for details.
\subsection{Trange}
The {\bf set trange} command sets the parametric range used to compute x and y
values when in parametric or polar modes.  Please see {\bf set xrange} for
details.
\subsection{Urange}
The {\bf set urange} and {\bf set vrange} commands set the parametric ranges used
to compute x, y, and z values when in {\bf splot} parametric mode.  Please see
{\bf set xrange} for details.
\subsection{Variables}
The {\bf show variables} command lists all user-defined variables and their
values.

Syntax:
\preverbatim
\begin{verbatim}
     show variables
\end{verbatim}
\postverbatim
\subsection{Version}
The {\bf show version} command lists the version of gnuplot being run, its last
modification date, the copyright holders, and email addresses for the FAQ,
the info-gnuplot mailing list, and reporting bugs--in short, the information
listed on the screen when the program is invoked interactively.

Syntax:
\preverbatim
\begin{verbatim}
     show version {long}
\end{verbatim}
\postverbatim

When the {\bf long} option is given, it also lists the operating system, the
compilation options used when {\bf gnuplot} was installed, the location of the
help file, and (again) the useful email addresses.
\subsection{View}
The {\bf set view} command sets the viewing angle for {\bf splot}s.  It controls how
the 3-d coordinates of the plot are mapped into the 2-d screen space.  It
provides controls for both rotation and scaling of the plotted data, but
supports orthographic projections only.

Syntax:
\preverbatim
\begin{verbatim}
     set view <rot_x> {,{<rot_z>}{,{<scale>}{,<scale_z>}}}
     show view
\end{verbatim}
\postverbatim

where $<$rot{\tt\_}x$>$ and $<$rot{\tt\_}z$>$ control the rotation angles (in degrees) in a
virtual 3-d coordinate system aligned with the screen such that initially
(that is, before the rotations are performed) the screen horizontal axis is
x, screen vertical axis is y, and the axis perpendicular to the screen is z.
The first rotation applied is $<$rot{\tt\_}x$>$ around the x axis.  The second rotation
applied is $<$rot{\tt\_}z$>$ around the new z axis.

$<$rot{\tt\_}x$>$ is bounded to the [0:180] range with a default of 60 degrees, while
$<$rot{\tt\_}z$>$ is bounded to the [0:360] range with a default of 30 degrees.
$<$scale$>$ controls the scaling of the entire {\bf splot}, while $<$scale{\tt\_}z$>$ scales
the z axis only.  Both scales default to 1.0.

Examples:
\preverbatim
\begin{verbatim}
     set view 60, 30, 1, 1
     set view ,,0.5
\end{verbatim}
\postverbatim

The first sets all the four default values.  The second changes only scale,
to 0.5.

See also {\bf set ticslevel}.
\subsection{Vrange}
The {\bf set urange} and {\bf set vrange} commands set the parametric ranges used
to compute x, y, and z values when in {\bf splot} parametric mode.  Please see
{\bf set xrange} for details.
\subsection{X2data}
The {\bf set x2data} command sets data on the x2 (top) axis to timeseries
(dates/times).  Please see {\bf set xdata}.
\subsection{X2dtics}
The {\bf set x2dtics} command changes tics on the x2 (top) axis to days of the
week.  Please see {\bf set xdtics} for details.
\subsection{X2label}
The {\bf set x2label} command sets the label for the x2 (top) axis.  Please see
{\bf set xlabel}.
\subsection{X2mtics}
The {\bf set x2mtics} command changes tics on the x2 (top) axis to months of the
year.  Please see {\bf set xmtics} for details.
\subsection{X2range}
The {\bf set x2range} command sets the horizontal range that will be displayed on
the x2 (top) axis.  Please see {\bf set xrange} for details.
\subsection{X2tics}
The {\bf set x2tics} command controls major (labelled) tics on the x2 (top) axis.
Please see {\bf set xtics} for details.
\subsection{X2zeroaxis}
The {\bf set x2zeroaxis} command draws a line at the origin of the x2 (top) axis
(y2 = 0).  For details, please see
{\bf set zeroaxis}.
\subsection{Xdata}
This command sets the datatype on the x axis to time/date.  A similar command
does the same thing for each of the other axes.

Syntax:
\preverbatim
\begin{verbatim}
     set xdata {time}
     show xdata
\end{verbatim}
\postverbatim

The same syntax applies to {\bf ydata}, {\bf zdata}, {\bf x2data} and {\bf y2data}.

The {\bf time} option signals that the datatype is indeed time/date.  If the
option is not specified, the datatype reverts to normal.

See {\bf set timefmt} to tell {\bf gnuplot} how to read date or time data.  The
time/date is converted to seconds from start of the century.  There is
currently only one timefmt, which implies that all the time/date columns must
confirm to this format.  Specification of ranges should be supplied as quoted
strings according to this format to avoid interpretation of the time/date as
an expression.

The function 'strftime' (type {\tt"}man strftime{\tt"} on unix to look it up) is used
to print tic-mark labels.  {\bf gnuplot} tries to figure out a reasonable format
for this  unless the {\bf set format x {\tt"}string{\tt"}} has supplied something that does
not look like a decimal format (more than one '\%' or neither \%f nor \%g).

See also {\bf Time/date} for more information.
\subsection{Xdtics}
The {\bf set xdtics} commands converts the x-axis tic marks to days of the week
where 0=Sun and 6=Sat.  Overflows are converted modulo 7 to dates.  {\bf set
noxdtics} returns the labels to their default values.  Similar commands do
the same things for the other axes.

Syntax:
\preverbatim
\begin{verbatim}
     set xdtics
     set noxdtics
     show xdtics
\end{verbatim}
\postverbatim

The same syntax applies to {\bf ydtics}, {\bf zdtics}, {\bf x2dtics} and {\bf y2dtics}.

See also the {\bf set format} command.
\subsection{Xlabel}
The {\bf set xlabel} command sets the x axis label.  Similar commands set labels
on the other axes.

Syntax:
\preverbatim
\begin{verbatim}
     set xlabel {"<label>"} {<xoff>}{,<yoff>} {"<font>{,<size>}"}
     show xlabel
\end{verbatim}
\postverbatim

The same syntax applies to {\bf x2label}, {\bf ylabel}, {\bf y2label} and {\bf zlabel}.

Specifying the constants $<$xoff$>$ or $<$yoff$>$ as optional offsets for a label
will move it $<$xoff$>$ or $<$yoff$>$ character widths or heights.  For example,
{\tt"}{\bf  set xlabel -1}{\tt"} will change only the x offset of the xlabel, moving the
label roughly one character width to the left.   The size of a character
depends on both the font and the terminal.

$<$font$>$ is used to specify the font in which the label is written; the units
of the font $<$size$>$ depend upon which terminal is used.

To clear a label, put no options on the command line, e.g., {\tt"}{\bf set y2label}{\tt"}.

The default positions of the axis labels are as follows:

xlabel:  The x-axis label is centered below the bottom axis.

ylabel:  The position of the y-axis label depends on the terminal, and can be
one of the following three positions:

1. Horizontal text flushed left at the top left of the plot.  Terminals that
cannot rotate text will probably use this method.  If {\bf set x2tics} is also
in use, the ylabel may overwrite the left-most x2tic label.  This may be
remedied by adjusting the ylabel position or the left margin.

2. Vertical text centered vertically at the left of the plot.  Terminals
that can rotate text will probably use this method.

3. Horizontal text centered vertically at the left of the plot.  The EEPIC,
LaTeX and TPIC drivers use this method.  The user must insert line breaks
using $\backslash$$\backslash$ to prevent the ylabel from overwriting the plot.  To produce a
vertical row of characters, add $\backslash$$\backslash$ between every printing character (but this
is ugly).

zlabel: The z-axis label is centered along the z axis and placed in the space
above the grid level.

y2label: The y2-axis label is placed to the right of the y2 axis.  The
position is terminal-dependent in the same manner as is the y-axis label.

x2label: The x2-axis label is placed above the top axis but below the plot
title.  It is also possible to create an x2-axis label by using new-line
characters to make a multi-line plot title, e.g.,

\preverbatim
\begin{verbatim}
     set title "This is the title\n\nThis is the x2label"
\end{verbatim}
\postverbatim

Note that double quotes must be used.  The same font will be used for both
lines, of course.

If you are not satisfied with the default position of an axis label, use {\bf set
label} instead--that command gives you much more control over where text is
placed.

Please see {\bf set syntax} for further information about backslash processing
and the difference between single- and double-quoted strings.
\subsection{Xmtics}
The {\bf set xmtics} commands converts the x-axis tic marks to months of the
year where 1=Jan and 12=Dec.  Overflows are converted modulo 12 to months.
The tics are returned to their default labels by {\bf set noxmtics}.  Similar
commands perform the same duties for the other axes.

Syntax:
\preverbatim
\begin{verbatim}
     set xmtics
     set noxmtics
     show xmtics
\end{verbatim}
\postverbatim

The same syntax applies to {\bf x2mtics}, {\bf ymtics}, {\bf y2mtics}, and {\bf zmtics}.

See also the {\bf set format} command.
\subsection{Xrange}
The {\bf set xrange} command sets the horizontal range that will be displayed.
A similar command exists for each of the other axes, as well as for the
polar radius r and the parametric variables t, u, and v.

Syntax:
\preverbatim
\begin{verbatim}
     set xrange [{{<min>}:{<max>}}] {{no}reverse} {{no}writeback}
     show xrange
\end{verbatim}
\postverbatim

where $<$min$>$ and $<$max$>$ terms are constants, expressions or an asterisk to set
autoscaling.  If the data are time/date, you must give the range as a quoted
string according to the {\bf set timefmt} format.  Any value omitted will not be
changed.

The same syntax applies to {\bf yrange}, {\bf zrange}, {\bf x2range}, {\bf y2range},
{\bf rrange}, {\bf trange}, {\bf urange} and {\bf vrange}.

The {\bf reverse} option reverses the direction of the axis, e.g., {\bf set xrange
[0:1] reverse} will produce an axis with 1 on the left and 0 on the right.
This is identical to the axis produced by {\bf set xrange [1:0]}, of course.
{\bf reverse} is intended primarily for use with {\bf autoscale}.

The {\bf writeback} option essentially saves the range found by {\bf autoscale} in
the buffers that would be filled by {\bf set xrange}.  This is useful if you wish
to plot several functions together but have the range determined by only
some of them.  The {\bf writeback} operation is performed during the {\bf plot}
execution, so it must be specified before that command.  For example,

\preverbatim
\begin{verbatim}
     set xrange [-10:10]
     set yrange [] writeback
     plot sin(x)
     set noautoscale y
     replot x/2
\end{verbatim}
\postverbatim

results in a yrange of [-1:1] as found only from the range of sin(x); the
[-5:5] range of x/2 is ignored.  Executing {\bf show yrange} after each command
in the above example should help you understand what is going on.

In 2-d, {\bf xrange} and {\bf yrange} determine the extent of the axes, {\bf trange}
determines the range of the parametric variable in parametric mode or the
range of the angle in polar mode.  Similarly in parametric 3-d, {\bf xrange},
{\bf yrange}, and {\bf zrange} govern the axes and {\bf urange} and {\bf vrange} govern the
parametric variables.

In polar mode, {\bf rrange} determines the radial range plotted.  $<$rmin$>$ acts as
an additive constant to the radius, whereas $<$rmax$>$ acts as a clip to the
radius --- no point with radius greater than $<$rmax$>$ will be plotted.  {\bf xrange}
and {\bf yrange} are affected --- the ranges can be set as if the graph was of
r(t)-rmin, with rmin added to all the labels.

Any range may be partially or totally autoscaled, although it may not make
sense to autoscale a parametric variable unless it is plotted with data.

Ranges may also be specified on the {\bf plot} command line.  A range given on
the plot line will be used for that single {\bf plot} command; a range given by
a {\bf set} command will be used for all subsequent plots that do not specify
their own ranges.  The same holds true for {\bf splot}.

Examples:

To set the xrange to the default:
\preverbatim
\begin{verbatim}
     set xrange [-10:10]
\end{verbatim}
\postverbatim

To set the yrange to increase downwards:
\preverbatim
\begin{verbatim}
     set yrange [10:-10]
\end{verbatim}
\postverbatim

To change zmax to 10 without affecting zmin (which may still be autoscaled):
\preverbatim
\begin{verbatim}
     set zrange [:10]
\end{verbatim}
\postverbatim

To autoscale xmin while leaving xmax unchanged:
\preverbatim
\begin{verbatim}
     set xrange [*:]
\end{verbatim}
\postverbatim
\subsection{Xtics}
Fine control of the major (labelled) tics on the x axis is possible with the
{\bf set xtics} command.  The tics may be turned off with the {\bf set noxtics}
command, and may be turned on (the default state) with {\bf set xtics}.  Similar
commands control the major tics on the y, z, x2 and y2 axes.

Syntax:
\preverbatim
\begin{verbatim}
     set xtics {axis | border} {{no}mirror} {{no}rotate}
               {  autofreq
                | <incr>
                | <start>, <incr> {,<end>}
                | ({"<label>"} <pos> {,{"<label>"} <pos>}...) }
     set noxtics
     show xtics
\end{verbatim}
\postverbatim

The same syntax applies to {\bf ytics}, {\bf ztics}, {\bf x2tics} and {\bf y2tics}.

{\bf axis} or {\bf border} tells {\bf gnuplot} to put the tics (both the tics themselves
and the accompanying labels) along the axis or the border, respectively.  If
the axis is very close to the border, the {\bf axis} option can result in tic
labels overwriting other text written in the margin.

{\bf mirror} tells {\bf gnuplot} to put unlabelled tics at the same positions on the
opposite border.  {\bf nomirror} does what you think it does.

{\bf rotate} asks {\bf gnuplot} to rotate the text through 90 degrees, which will be
done if the terminal driver in use supports text rotation.  {\bf norotate}
cancels this.

The defaults are {\bf border mirror norotate} for tics on the x and y axes, and
{\bf border nomirror norotate} for tics on the x2 and y2 axes.  For the z axis,
the the {\bf \{axis $|$ border\}} option is not available and the default is
{\bf nomirror}.  If you do want to mirror the z-axis tics, you might want to
create a bit more room for them with {\bf set border}.

{\bf set xtics} with no options restores the default border or axis if xtics are
being displayed;  otherwise it has no effect.  Any previously specified tic
frequency or position \{and labels\} are retained.

Positions of the tics are calculated automatically by default or if the
{\bf autofreq} option is given; otherwise they may be specified in either of
two forms:

The implicit $<$start$>$, $<$incr$>$, $<$end$>$ form specifies that a series of tics will
be plotted on the axis between the values $<$start$>$ and $<$end$>$ with an increment
of $<$incr$>$.  If $<$end$>$ is not given, it is assumed to be infinity.  The
increment may be negative.  If neither $<$start$>$ nor $<$end$>$ is given, $<$start$>$ is
assumed to be negative infinity, $<$end$>$ is assumed to be positive infinity,
and the tics will be drawn at integral multiples of $<$step$>$.  If the axis is
logarithmic, the increment will be used as a multiplicative factor.

Examples:

Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.
\preverbatim
\begin{verbatim}
     set xtics 0,.5,10
\end{verbatim}
\postverbatim

Make tics at ..., -10, -5, 0, 5, 10, ...
\preverbatim
\begin{verbatim}
     set xtics 5
\end{verbatim}
\postverbatim

Make tics at 1, 100, 1e4, 1e6, 1e8.
\preverbatim
\begin{verbatim}
     set logscale x; set xtics 1,100,10e8
\end{verbatim}
\postverbatim

The explicit ({\tt"}$<$label$>${\tt"} $<$pos$>$, ...) form allows arbitrary tic positions or
non-numeric tic labels.  A set of tics is a set of positions, each with its
own optional label.  Note that the label is a string enclosed by quotes.  It
may be a constant string, such as {\tt"}hello{\tt"}, may contain formatting information
for converting the position into its label, such as {\tt"}\%3f clients{\tt"}, or may be
empty, {\tt"}{\tt"}.  See {\bf set format} for more information.  If no string is given,
the default label (numerical) is used.  In this form, the tics do not need to
be listed in numerical order.

Examples:
\preverbatim
\begin{verbatim}
     set xtics ("low" 0, "medium" 50, "high" 100)
     set xtics (1,2,4,8,16,32,64,128,256,512,1024)
     set ytics ("bottom" 0, "" 10, "top" 20)
\end{verbatim}
\postverbatim

In the second example, all tics are labelled.  In the third, only the end
tics are labelled.

However they are specified, tics will only be plotted when in range.

Format (or omission) of the tic labels is controlled by {\bf set format}, unless
the explicit text of a labels is included in the {\bf set xtic (}$<$label$>${\bf )} form.

Minor (unlabelled) tics can be added by the {\bf set mxtics} command.

In case of timeseries data, position values must be given as quoted dates
or times according to the format {\bf timefmt}.  If the $<$start$>$, $<$incr$>$, $<$end$>$
form is used, $<$start$>$ and $<$end$>$ must be given according to {\bf timefmt}, but
$<$incr$>$ must be in seconds.  Times will be written out according to the format
given on {\bf set format}, however.

Examples:
\preverbatim
\begin{verbatim}
     set xdata time
     set timefmt "%d/%m"
     set format x "%b %d"
     set xrange ["01/12":"06/12"]
     set xtics "01/12", 172800, "05/12"
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     set xdata time
     set timefmt "%d/%m"
     set format x "%b %d"
     set xrange ["01/12":"06/12"]
     set xtics ("01/12", "" "03/12", "05/12")
\end{verbatim}
\postverbatim
Both of these will produce tics {\tt"}Dec 1{\tt"}, {\tt"}Dec 3{\tt"}, and {\tt"}Dec 5{\tt"}, but in the
second example the tic at {\tt"}Dec 3{\tt"} will be unlabelled.

\subsection{Xzeroaxis}
The {\bf set xzeroaxis} command draws a line at y = 0.  For details, please see
{\bf set zeroaxis}.
\subsection{Y2data}
The {\bf set y2data} command sets y2 (right-hand) axis data to timeseries
(dates/times).  Please see {\bf set xdata}.
\subsection{Y2dtics}
The {\bf set y2dtics} command changes tics on the y2 (right-hand) axis to days of
the week.  Please see {\bf set xdtics} for details.
\subsection{Y2label}
The {\bf set y2dtics} command sets the label for the y2 (right-hand) axis.
Please see {\bf set xlabel}.
\subsection{Y2mtics}
The {\bf set y2mtics} command changes tics on the y2 (right-hand) axis to months
of the year.  Please see {\bf set xmtics} for details.
\subsection{Y2range}
The {\bf set y2range} command sets the vertical range that will be displayed on
the y2 (right-hand) axis.  Please see {\bf set xrange} for details.
\subsection{Y2tics}
The {\bf set y2tics} command controls major (labelled) tics on the y2 (right-hand)
axis.  Please see {\bf set xtics} for details.
\subsection{Y2zeroaxis}
The {\bf set y2zeroaxis} command draws a line at the origin of the y2 (right-hand)
axis (x2 = 0).  For details, please see {\bf set zeroaxis}.
\subsection{Ydata}
Sets y-axis data to timeseries (dates/times).  Please see {\bf set xdata}.
\subsection{Ydtics}
The {\bf set ydtics} command changes tics on the y axis to days of the week.
Please see {\bf set xdtics} for details.
\subsection{Ylabel}
This command sets the label for the y axis.  Please see {\bf set xlabel}.
\subsection{Ymtics}
The {\bf set ymtics} command changes tics on the y axis to months of the year.
Please see {\bf set xmtics} for details.
\subsection{Yrange}
The {\bf set yrange} command sets the vertical range that will be displayed on
the y axis.  Please see {\bf set xrange} for details.
\subsection{Ytics}
The {\bf set ytics} command controls major (labelled) tics on the y axis.
Please see {\bf set xtics} for details.
\subsection{Yzeroaxis}
The {\bf set yzeroaxis} command draws a line at x = 0.  For details, please see
{\bf set zeroaxis}.
\subsection{Zdata}
Set zaxis date to timeseries (dates/times).  Please see {\bf set xdata}.
\subsection{Zdtics}
The {\bf set zdtics} command changes tics on the z axis to days of the week.
Please see {\bf set xdtics} for details.
\subsection{Zero}
The {\bf zero} value is the default threshold for values approaching 0.0.

Syntax:
\preverbatim
\begin{verbatim}
     set zero <expression>
     show zero
\end{verbatim}
\postverbatim

{\bf gnuplot} will not plot a point if its imaginary part is greater in magnitude
than the {\bf zero} threshold.  This threshold is also used in various other
parts of {\bf gnuplot} as a (crude) numerical-error threshold.  The default
{\bf zero} value is 1e-8.  {\bf zero} values larger than 1e-3 (the reciprocal of the
number of pixels in a typical bitmap display) should probably be avoided, but
it is not unreasonable to set {\bf zero} to 0.0.
\subsection{Zeroaxis}
The x axis may be drawn by {\bf set xzeroaxis} and removed by {\bf set noxzeroaxis}.
Similar commands behave similarly for the y, x2, and y2 axes.

Syntax:
\preverbatim
\begin{verbatim}
     set {x|x2|y|y2|}zeroaxis { {linestyle | ls <line_style>}
                                | { linetype | lt <line_type>}
                                  { linewidth | lw <line_width>}}
     set no{x|x2|y|y2|}zeroaxis
     show {x|y|}zeroaxis
\end{verbatim}
\postverbatim


By default, these options are off.  The selected zero axis is drawn
with a line of type $<$line{\tt\_}type$>$ and width $<$line{\tt\_}width$>$ (if supported
by the terminal driver currently in use), or a user-defined style
$<$line{\tt\_}style$>$.

If no linetype is specified, any zero axes selected will be drawn
using the axis linetype (linetype 0).

{\bf set zeroaxis l} is equivalent to {\bf set xzeroaxis l; set yzeroaxis l}. {\bf set
nozeroaxis} is equivalent to {\bf set noxzeroaxis; set noyzeroaxis}.
\subsection{Zlabel}
This command sets the label for the z axis.  Please see {\bf set xlabel}.
\subsection{Zmtics}
The {\bf set zmtics} command changes tics on the z axis to months of the year.
Please see {\bf set xmtics} for details.
\subsection{Zrange}
The {\bf set zrange} command sets the range that will be displayed on the z axis.
The zrange is used only by {\bf splot} and is ignored by {\bf plot}.  Please see {\bf set
xrange} for details.
\subsection{Ztics}
The {\bf set ztics} command controls major (labelled) tics on the z axis.
Please see {\bf set xtics} for details.
\section{Shell}
The {\bf shell} command spawns an interactive shell.  To return to {\bf gnuplot},
type {\bf logout} if using VMS, {\bf exit} or the END-OF-FILE character if using
Unix, {\bf endcli} if using AmigaOS, or {\bf exit} if using MS-DOS or OS/2.

A single shell command may be spawned by preceding it with the ! character
(\$ if using VMS) at the beginning of a command line.  Control will return
immediately to {\bf gnuplot} after this command is executed.  For example, in
Unix, AmigaOS, MS-DOS or OS/2,

\preverbatim
\begin{verbatim}
     ! dir
\end{verbatim}
\postverbatim

prints a directory listing and then returns to {\bf gnuplot}.

On an Atari, the {\bf !} command first checks whether a shell is already loaded
and uses it, if available.  This is practical if {\bf gnuplot} is run from
{\bf gulam}, for example.
\section{Splot}
{\bf splot} is the command for drawing 3-d plots (well, actually projections on
a 2-d surface, but you knew that).  It can create a plot from functions or
a data file in a manner very similar to the {\bf plot} command.

See {\bf plot} for features common to the {\bf plot} command; only differences are
discussed in detail here.  Note specifically that the {\bf binary} and {\bf matrix}
options (discussed under {\tt"}datafile-modifiers{\tt"}) are not available for {\bf plot}.

Syntax:
\preverbatim
\begin{verbatim}
     splot {<ranges>}
           <function> | "<datafile>" {datafile-modifiers}}
           {<title-spec>} {with <style>}
           {, {definitions,} <function> ...}
\end{verbatim}
\postverbatim

where either a $<$function$>$ or the name of a data file enclosed in quotes is
supplied.  The function can be a mathematical expression, or a triple of
mathematical expressions in parametric mode.

By default {\bf splot} draws the xy plane completely below the plotted data.
The offset between the lowest ztic and the xy plane can be changed by {\bf set
ticslevel}.  The orientation of a {\bf splot} projection is controlled by
{\bf set view}.  See {\bf set view} and {\bf set ticslevel} for more information.

The syntax for setting ranges on the {\bf splot} command is the same as for
{\bf plot}.  In non-parametric mode, the order in which ranges must be given is
{\bf xrange}, {\bf yrange}, and {\bf zrange}.  In parametric mode, the order is {\bf urange},
{\bf vrange}, {\bf xrange}, {\bf yrange}, and {\bf zrange}.

The {\bf title} option is the same as in {\bf plot}.  The operation of {\bf with} is also
the same as in {\bf plot}, except that the plotting styles available to {\bf splot}
are limited to {\bf lines}, {\bf points}, {\bf linespoints}, {\bf dots}, and {\bf impulses};  the
error-bar capabilities of {\bf plot} are not available for {\bf splot}.

The datafile options have more differences.
\subsection{Data-file}
As for {\bf plot}, discrete data contained in a file can be displayed by
specifying the name of the data file, enclosed in quotes,  on the {\bf splot}
command line.

Syntax:
\preverbatim
\begin{verbatim}
     splot '<file_name>' {binary | matrix}
                         {index <index list>}
                         {every <every list>}
                         {using <using list>}
\end{verbatim}
\postverbatim

The special filenames {\bf {\tt"}{\tt"}} and {\bf {\tt"}-{\tt"}} are permitted, as in {\bf plot}.

In brief, {\bf binary} and {\bf matrix} indicate that the the data are in a special
form, {\bf index} selects which data sets in a multi-data-set file are to be
plotted, {\bf every} specifies which datalines (subsets) within a single data
set are to be plotted, and {\bf using} determines how the columns within a single
record are to be interpreted.

The options {\bf index} and {\bf every} behave the same way as with {\bf plot};  {\bf using}
does so also, except that the {\bf using} list must provide three entries
instead of two.

The {\bf plot} options {\bf thru} and {\bf smooth} are not available for {\bf splot}, but
{\bf cntrparams} and {\bf dgrid3d} provide limited smoothing cabilities.

Data file organization is essentially the same as for {\bf plot}, except that
each point is an (x,y,z) triple.  If only a single value is provided, it
will be used for z, the datablock number will be used for y, and the index
of the data point in the datablock will be used for x.  If two values are
provided, {\bf gnuplot} gives you an error message.  Three values are interpreted
as an (x,y,z) triple.  Additional values are generally used as errors, which
can be used by {\bf fit}.

Single blank records separate datablocks in a {\bf splot} datafile; {\bf splot}
treats datablocks as the equivalent of function y-isolines.  No line will
join points separated by a blank record.  If all datablocks contain the same
number of points, {\bf gnuplot} will draw cross-isolines between datablocks,
connecting corresponding points.  This is termed {\tt"}grid data{\tt"}, and is required
for drawing a surface, for contouring ({\bf set contour}) and hidden-line removal
({\bf set hidden3d}). See also {\bf splot grid data}

It is no longer necessary to specify {\bf parametric} mode for three-column
{\bf splot}s.
\subsubsection{Binary}
{\bf splot} can read binary files written with a specific format (and on a
system with a compatible binary file representation.)

In previous versions, {\bf gnuplot} dynamically detected binary data files.  It
is now necessary to specify the keyword {\bf binary} directly after the filename.

Single precision floats are stored in a binary file as follows:

\preverbatim
\begin{verbatim}
     <N+1>  <y0>   <y1>   <y2>  ...  <yN>
      <x0> <z0,0> <z0,1> <z0,2> ... <z0,N>
      <x1> <z1,0> <z1,1> <z1,2> ... <z1,N>
       :      :      :      :   ...    :
\end{verbatim}
\postverbatim

which are converted into triplets:
\preverbatim
\begin{verbatim}
     <x0> <y0> <z0,0>
     <x0> <y1> <z0,1>
     <x0> <y2> <z0,2>
      :    :     :
     <x0> <yN> <z0,N>
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
     <x1> <y0> <z1,0>
     <x1> <y1> <z1,1>
      :    :     :
\end{verbatim}
\postverbatim

These triplets are then converted into {\bf gnuplot} iso-curves and then
{\bf gnuplot} proceeds in the usual manner to do the rest of the plotting.

A collection of matrix and vector manipulation routines (in C) is provided
in {\bf binary.c}.  The routine to write binary data is

\preverbatim
\begin{verbatim}
     int fwrite_matrix(file,m,nrl,nrl,ncl,nch,row_title,column_title)
\end{verbatim}
\postverbatim

An example of using these routines is provided in the file {\bf bf{\tt\_}test.c}, which
generates binary files for the demo file {\bf demo/binary.dem}.

The {\bf index} keyword is not supported, since the file format allows only one
surface per file.  The {\bf every} and {\bf using} filters are supported.  {\bf using}
operates as if the data were read in the above triplet form.
\subsubsection{Example datafile}
A simple example of plotting a 3-d data file is

\preverbatim
\begin{verbatim}
     splot 'datafile.dat'
\end{verbatim}
\postverbatim

where the file {\tt"}datafile.dat{\tt"} might contain:

\preverbatim
\begin{verbatim}
     # The valley of the Gnu.
        0 0 10
        0 1 10
        0 2 10
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
        1 0 10
        1 1 5
        1 2 10
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
        2 0 10
        2 1 1
        2 2 10
\end{verbatim}
\postverbatim

\preverbatim
\begin{verbatim}
        3 0 10
        3 1 0
        3 2 10
\end{verbatim}
\postverbatim

Note that {\tt"}datafile.dat{\tt"} defines a 4 by 3 grid ( 4 rows of 3 points each ).
Rows (datablocks) are separated by blank records.

Note also that the x value is held constant within each dataline.  If you
instead keep y constant, and plot with hidden-line removal enabled, you will
find that the surface is drawn 'inside-out'.

Actually for grid data it is not necessary to keep the x values constant
within a datablock, nor is it necessary to keep the same sequence of y
values.  {\bf gnuplot} requires only that the number of points be the same for
each datablock.  However since the surface mesh, from which contours are
derived, connects sequentially corresponding points, the effect of an
irregular grid on a surface plot is unpredictable and should be examined
on a case-by-case basis.
\subsubsection{Matrix}
The {\bf matrix} flag indicates that the ASCII data are stored in matrix format.
The z-values are read in a row at a time, i. e.,
\preverbatim
\begin{verbatim}
     z11 z12 z13 z14 ...
     z21 z22 z23 z24 ...
     z31 z32 z33 z34 ...
\end{verbatim}
\postverbatim
and so forth.  The row and column indices are used for the x- and y-values.
\subsection{Grid{\tt\_}data}
The 3D routines are designed for points in a grid format, with one sample,
datapoint, at each mesh intersection; the datapoints may originate from
either evaluating a function, see {\bf set isosamples}, or reading a datafile,
see {\bf splot datafile}.  The term {\tt"}isoline{\tt"} is applied to the mesh lines for
both functions and data.  Note that the mesh need not be rectangular in x
and y, as it may be parameterized in u and v, see {\bf set isosamples}.

However, {\bf gnuplot} does not require that format.  In the case of functions,
'samples' need not be equal to 'isosamples', i.e., not every x-isoline
sample need intersect a y-isoline. In the case of data files, if there
are an equal number of scattered data points in each datablock, then
{\tt"}isolines{\tt"} will connect the points in a datablock, and {\tt"}cross-isolines{\tt"}
will connect the corresponding points in each datablock to generate a
{\tt"}surface{\tt"}.  In either case, contour and hidden3d modes may give different
plots than if the points were in the intended format.  Scattered data can be
converted to a \{different\} grid format with {\bf set dgrid3d}.

The contour code tests for z intensity along a line between a point on a
y-isoline and the corresponding point in the next y-isoline.  Thus a {\bf splot}
contour of a surface with samples on the x-isolines that do not coincide with
a y-isoline intersection will ignore such samples. Try:
\preverbatim
\begin{verbatim}
      set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
      set function style lp
      set contour
      set isosamples 10,10; set samples 10,10;
      splot cos(x)*cos(y)
      set samples 4,10; replot
      set samples 10,4; replot
\end{verbatim}
\postverbatim

\subsection{Splot{\tt\_}overview}
{\bf splot} can display a surface as a collection of points, or by connecting
those points.  As with {\bf plot}, the points may be read from a data file or
result from evaluation of a function at specified intervals, see {\bf set
isosamples}.  The surface may be approximated by connecting the points
with straight line segments, see {\bf set surface}, in which case the surface
can be made opaque with {\bf set hidden3d.}  The orientation from which the 3d
surface is viewed can be changed with {\bf set view}.

Additionally, for points in a grid format, {\bf splot} can interpolate points
having a common amplitude (see {\bf set contour}) and can then connect those
new points to display contour lines, either directly with straight-line
segments or smoothed lines (see {\bf set cntrparams}).  Functions are already
evaluated in a grid format, determined by {\bf set isosamples} and {\bf set samples},
while file data must either be in a grid format, as described in {\bf data-file},
or be used to generate a grid (see {\bf set dgrid3d}).

Contour lines may be displayed either on the surface or projected onto the
base.  The base projections of the contour lines may be written to a
file, and then read with {\bf plot}, to take advantage of {\bf plot}'s additional
formatting capabilities.
\section{Test}
{\bf test} creates a display of line and point styles and other useful things
appropriate for the terminal you are using.

Syntax:
\preverbatim
\begin{verbatim}
     test
\end{verbatim}
\postverbatim
\section{Update}
This command writes the current values of the fit parameters into the given
file, formatted as an initial-value file (as described in the {\bf fit}section).
This is useful for saving the current values for later use or for restarting
a converged or stopped fit.

Syntax:
\preverbatim
\begin{verbatim}
     update <filename> {<filename>}
\end{verbatim}
\postverbatim

If a second filename is supplied, the updated values are written to this
file, and the original parameter file is left unmodified.

Otherwise, if the file already exists, {\bf gnuplot} first renames it by
appending {\bf .old} and then opens a new file.  That is, {\tt"}{\bf update 'fred'}{\tt"}
behaves the same as {\tt"}{\bf !rename fred fred.old; update 'fred.old' 'fred'}{\tt"}.
[On DOS and other systems that use the twelve-character {\tt"}filename.ext{\tt"}
naming convention, {\tt"}ext{\tt"} will be {\tt"}{\bf old}{\tt"} and {\tt"}filename{\tt"} will be related
(hopefully recognizably) to the initial name.  Renaming is not done at all
on VMS systems, since they use file-versioning.]

Please see {\bf fit} for more information.
\part{Graphical User Interfaces}
Several graphical user interfaces have been written for {\bf gnuplot} and one for
win32 is included in this distribution.  In addition, there is a Macintosh
interface at
\preverbatim
\begin{verbatim}
      ftp://ftp.ee.gatech.edu/pub/mac/gnuplot
\end{verbatim}
\postverbatim
and several X11 interfaces include three Tcl/Tk located at the usual Tcl/Tk
repositories.
\part{Bugs}
Floating point exceptions (floating point number too large/small, divide by
zero, etc.) may occasionally be generated by user defined functions.  Some of
the demos in particular may cause numbers to exceed the floating point range.
Whether the system ignores such exceptions (in which case {\bf gnuplot} labels
the corresponding point as undefined) or aborts {\bf gnuplot} depends on the
compiler/runtime environment.

The bessel functions do not work for complex arguments.

The gamma function does not work for complex arguments.

As of {\bf gnuplot} version 3.7, all development has been done using ANSI C.
With current operating system, compiler, and library releases, the OS
specific bugs documented in release 3.5, now relegated to {\bf old{\tt\_}bugs}, may
no longer be relevant.

Bugs reported since the current release may be located via the official
distribution site:
\preverbatim
\begin{verbatim}
      ftp://ftp.dartmouth.edu/pub/gnuplot
     http://www.cs.dartmouth.edu/gnuplot_info.html
\end{verbatim}
\postverbatim

Please e-mail any bugs to bug-gnuplot@dartmouth.edu.
\section{Old{\tt\_}bugs}
There is a bug in the stdio library for old Sun operating systems (SunOS
Sys4-3.2).  The {\tt"}\%g{\tt"} format for 'printf' sometimes incorrectly prints numbers
(e.g., 200000.0 as {\tt"}2{\tt"}).  Thus, tic mark labels may be incorrect on a Sun4
version of {\bf gnuplot}.  A work-around is to rescale the data or use the {\bf set
format} command to change the tic mark format to {\tt"}\%7.0f{\tt"} or some other
appropriate format.  This appears to have been fixed in SunOS 4.0.

Another bug: On a Sun3 under SunOS 4.0, and on Sun4's under Sys4-3.2 and
SunOS 4.0, the 'sscanf' routine incorrectly parses {\tt"}00 12{\tt"} with the format
{\tt"}\%f \%f{\tt"} and reads 0 and 0 instead of 0 and 12.  This affects data input.  If
the data file contains x coordinates that are zero but are specified like
'00', '000', etc, then you will read the wrong y values.  Check any data
files or upgrade the SunOS.  It appears to have been fixed in SunOS 4.1.1.

Suns appear to overflow when calculating exp(-x) for large x, so {\bf gnuplot}
gets an undefined result.  One work-around is to make a user-defined function
like e(x) = x$<$-500 ? 0 : exp(x).  This affects plots of Gaussians (exp(-x*x))
in particular, since x*x grows quite rapidly.

Microsoft C 5.1 has a nasty bug associated with the \%g format for 'printf'.
When any of the formats {\tt"}\%.2g{\tt"}, {\tt"}\%.1g{\tt"}, {\tt"}\%.0g{\tt"}, {\tt"}\%.g{\tt"} are used, 'printf' will
incorrectly print numbers in the range 1e-4 to 1e-1.  Numbers that should be
printed in the \%e format are incorrectly printed in the \%f format, with the
wrong number of zeros after the decimal point.  To work around this problem,
use the \%e or \%f formats explicitly.

{\bf gnuplot}, when compiled with Microsoft C, did not work correctly on two VGA
displays that were tested.  The CGA, EGA and VGA drivers should probably be
rewritten to use the Microsoft C graphics library.  {\bf gnuplot} compiled with
Borland C++ uses the Turbo C graphics drivers and does work correctly with
VGA displays.

VAX/VMS 4.7 C compiler release 2.4 also has a poorly implemented \%g format
for 'printf'.  The numbers are printed numerically correct, but may not be in
the requested format.  The K\&R second edition says that for the \%g format, \%e
is used if the exponent is less than -4 or greater than or equal to the
precision.  The VAX uses \%e format if the exponent is less than -1.  The VAX
appears to take no notice of the precision when deciding whether to use \%e or
\%f for numbers less than 1.  To work around this problem, use the \%e or \%f
formats explicitly.  From the VAX C 2.4 release notes: e,E,f,F,g,G  Result
will always contain a decimal  point.  For g and G, trailing zeros will not
be removed from the result.

VAX/VMS 5.2 C compiler release 3.0 has a slightly better implemented \%g
format than release 2.4, but not much.  Trailing decimal points are now
removed, but trailing zeros are still not removed from \%g numbers in
exponential format.

The two preceding problems are actually in the libraries rather than in the
compilers.  Thus the problems will occur whether {\bf gnuplot} is built using
either the DEC compiler or some other one (e.g. the latest gcc).

ULTRIX X11R3 has a bug that causes the X11 driver to display {\tt"}every other{\tt"}
graph.  The bug seems to be fixed in DEC's release of X11R4 so newer releases
of ULTRIX don't seem to have the problem.  Solutions for older sites include
upgrading the X11 libraries (from DEC or direct from MIT) or defining
ULTRIX{\tt\_}KLUDGE when compiling the x11.trm file.  Note that the kludge is not
an ideal fix, however.

The constant HUGE was incorrectly defined in the NeXT OS 2.0 operating
system.  HUGE should be set to 1e38 in plot.h. This error has been corrected
in the 2.1 version of NeXT OS.

Some older models of HP plotters do not have a page eject command 'PG'.  The
current HPGL driver uses this command in HPGL{\tt\_}reset.  This may need to be
removed for these plotters.  The current PCL5 driver uses HPGL/2 for text as
well as graphics.  This should be modified to use scalable PCL fonts.

On the Atari version, it is not possible to send output directly to the
printer (using {\bf /dev/lp} as output file), since CRs are added to LFs in
binary output.  As a work-around, write the output to a file and copy it to
the printer afterwards using a shell command.

On AIX 4, the literal 'NaNq' in a datafile causes the special internal value
'not-a-number' to be stored, rather than setting an internal 'undefined'
flag.  A workaround is to use {\bf set missing 'NaNq'}.

There may be an up-to-date list of bugs since the release on the WWW page:
\preverbatim
\begin{verbatim}
     http://www.cs.dartmouth.edu/gnuplot_info.html
\end{verbatim}
\postverbatim

Please report any bugs to bug-gnuplot@dartmouth.edu.
\end{document}
