The C Users' Group Library 1994 August/wc-cdrom-cusersgrouplibrary-1994-08.iso/vol_300/334_01/gnuplot.doc

Text File | 1991-02-05 | 60KB | 1,643 lines

1 gnuplot
?
 GNUPLOT is a command-driven interactive function 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, separated by semicolons (;).

 Any command-line arguments are assumed to be names of files containing
 gnuplot commands, with the exception of standard X11 arguments, which
 are processed first. Each file is loaded with the `load` command, in the
 order specified. Gnuplot exits after the last file is processed.

 Commands may extend over several input lines, by ending each line but
 the last with a backslash (\). The backslash must be the 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 `comment`).

 In this documentation, curly braces ({}) denote optional arguments to
 many commands.

 For help on any topic, type 'help' followed by the name of the topic.
2 cd
?cd
 The `cd` command changes working directory.

 Syntax:
         cd <directory-name>

 The directory name must be enclosed in quotes.

 Examples:

         cd 'subdir'
         cd ".."
2 clear
?clear
 The `clear` command erases the current screen or output device as
 specified by `set output`.  This usually generates a formfeed on
 hardcopy devices.  Use `set terminal` to set the device type.
2 comment
?comments
 Comments are supported as follows: a # may appear in most places in a line
 and 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.
2 environment
?environment
 A number of shell environment variables are understood by 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 GNUPLOT on start
 up, but is itself overridden by the .gnuplot (or equivalent) start-up
 file (see help start-up), and of course by later explicit changes.

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

 On VMS, the symbol GNUPLOT$HELP should be defined as the name of
 the help library for gnuplot.

 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 MS-DOS, GNUPLOT is used.  On VMS, SYS$LOGIN: is used.
 See help start-up.

 On Unix, PAGER is used as an output filter for help messages. SHELL
 is used for the `shell` command.

 On MS-DOS, COMSPEC is used for the `shell` command.
2 exit
?exit
?quit
 The commands `exit` and `quit` and your computer's END-OF-FILE character
 will exit GNUPLOT.  All these commands will clear the output device
 (as the `clear` command does) before exiting.
2 expressions
?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 may be expressed as the {<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.
3 functions
?expressions functions
?functions
 The functions in 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.  The `sgn`
 function is also supported, as in BASIC.
@start table
#Function & Arguments & Returns \\ \hline
%Function@Arguments@Returns
%_
4 abs
?expressions functions abs
?functions abs
?abs
#abs(x) & any  &  absolute value of {\tt x}, $|x|$; same type \\
#abs(x) & complex &  length of {\tt x}, $\sqrt{{\mbox{real}(x)^{2} +
#\mbox{imag}(x)^{2}}}$ \\
%abs(x)@any@absolute value of x, $|x|$; same type
%abs(x)@complex@length of x, $sqrt{real (x) sup 2 + imag (x) sup 2}$
 The `abs` function returns the absolute value of its argument.  The
 returned value is of the same type as the argument.

 For complex arguments, abs(x) is defined as the length of x in the
 complex plane [i.e.,  sqrt(real(x)**2 + imag(x)**2) ].
4 acos
?expressions functions acos
?functions acos
?acos
#acos(x) & any  & $\cos^{-1} x$ (inverse cosine) in radians \\
%acos(x)@any@$cos sup -1 x$ (inverse cosine) in radians
 The `acos` function returns the arc cosine (inverse cosine) of its
 argument.  `acos` returns its argument in radians.
4 arg
?expressions functions arg
?functions arg
?arg
#arg(x) & complex & the phase of $x$ in radians\\
%arg(x)@complex@the phase of $x$ in radians
 The `arg` function returns the phase of a complex number, in radians.
4 asin
?expressions functions asin
?functions asin
?asin
#asin(x) & any  & $\sin^{-1} x$ (inverse sin) in radians \\
%asin(x)@any@$sin sup -1 x$ (inverse sin) in radians
 The `asin` function returns the arc sin (inverse sin) of its argument.
 `asin` returns its argument in radians.
4 atan
?expressions functions atan
?functions atan
?atan
#atan(x) & any  & $\tan^{-1} x$ (inverse tangent) in radians \\
%atan(x)@any@$tan sup -1 x$ (inverse tangent) in radians
 The `atan` function returns the arc tangent (inverse tangent) of its
 argument.  `atan` returns its argument in radians.
4 besj0
?expressions functions besj0
?functions besj0
?besj0
#besj0(x) & radians &  $j_{0}$ Bessel function of $x$ \\
%besj0(x)@radians@$j sub 0$ Bessel function of $x$
 The `besj0` function returns the j0th Bessel function of its argument.
 `besj0` expects its argument to be in radians.
4 besj1
?expressions functions besj1
?functions besj1
?besj1
#besj1(x) & radians & $j_{1}$ Bessel function of $x$ \\
%besj1(x)@radians@$j sub 1$ Bessel function of $x$
 The `besj1` function returns the j1st Bessel function of its argument.
 `besj1` expects its argument to be in radians.
4 besy0
?expressions functions besy0
?functions besy0
?besy0
#besy0(x) & radians & $y_{0}$ Bessel function of $x$ \\
%besy0(x)@radians@$y sub 0$ Bessel function of $x$
 The `besy0` function returns the y0th Bessel function of its argument.
 `besy0` expects its argument to be in radians.
4 besy1
?expressions functions besy1
?functions besy1
?besy1
#besy1(x) & radians & $y_{1}$ Bessel function of $x$ \\
%besy1(x)@radians@$y sub 1$ Bessel function of $x$
 The `besy1` function returns the y1st Bessel function of its argument.
 `besy1` expects its argument to be in radians.
4 ceil
?expressions functions ceil
?functions ceil
?ceil
#ceil(x) & any & $\lceil x \rceil$, smallest integer not less than $x$
#(real part) \\
%ceil(x)@any@$left ceiling x right ceiling$, smallest integer not less than $x$ (real part)
 The `ceil` function returns the smallest integer that is not less than its
 argument.  For complex numbers, `ceil` returns the smallest integer
 not less than the real part of its argument.
4 cos
?expressions functions cos
?functions cos
?cos
#cos(x) & radians & $\cos x$, cosine of $x$ \\
%cos(x)@radians@$cos~x,$ cosine of $x$
 The `cos` function returns the cosine of its argument.  `cos` expects its
 argument to be in radians.
4 cosh
?expressions functions cosh
?functions cosh
?cosh
#cosh(x) & radians & $\cosh x$, hyperbolic cosine of $x$ \\
%cosh(x)@radians@$cosh~x,$ hyperbolic cosine of $x$
 The `cosh` function returns the hyperbolic cosine of its argument.
 `cosh` expects its argument to be in radians.
4 exp
?expressions functions exp
?functions exp
?exp
#exp(x) & any & $e^{x}$,  exponential function of $x$ \\
%exp(x)@any@$e sup x$, exponential function of $x$
 The `exp` function returns the exponential function of its argument
 (`e` raised to the power of its argument).
4 floor
?expressions functions floor
?functions floor
?floor
#floor(x) & any & $\lfloor x \rfloor$,  largest integer not greater
#than $x$ (real part) \\
%floor(x)@any@$left floor x right floor$, largest integer not greater than $x$ (real part)
 The `floor` function returns the largest integer not greater than its
 argument.  For complex numbers, `floor` returns the largest
 integer not greater than the real part of its argument.
4 imag
?expressions functions imag
?functions imag
?imag
#imag(x) & complex &  imaginary part of $x$ as a real number \\
%imag(x)@complex@imaginary part of $x$ as a real number
 The `imag` function returns the imaginary part of its argument as a
 real number.
4 int
?expressions functions int
?functions int
?int
#int(x) & real &  integer part of $x$, truncated toward zero \\
%int(x)@real@integer part of $x,$ truncated toward zero
 The `int` function returns the integer part of its argument, truncated
 toward zero.
4 log
?expressions functions log
?functions log
?log
#log(x) & any & $\log_{e} x$,  natural logarithm (base $e$) of $x$ \\
%log(x)@any@$ln~x,$ natural logarithm (base $e$) of $x$
 The `log` function returns the natural logarithm (base `e`) of its
 argument.
4 log10
?expressions functions log10
?functions log10
?log10
#log10(x) & any & $\log_{10} x$,  logarithm (base $10$) of $x$ \\
%log10(x)@any@${log sub 10}~x,$ logarithm (base $10$) of $x$
 The `log10` function returns the logarithm (base 10) of its argument.
4 real
?expressions functions real
?functions real
?real
#real(x) & any &  real part of $x$ \\
%real(x)@any@real part of $x$
 The `real` function returns the real part of its argument.
4 sgn
?expressions functions sgn
?functions sgn
?sgn
#sgn(x) & any & 1 if $x>0$, -1 if $x<0$, 0 if $x=0$. imag($x$) ignored \\
%sgn(x)@any@1 if $x > 0$, -1 if $x < 0$, 0 if $x = 0$. $imag (x)$ ignored
 The `sgn` function returns 1 if its argument is positive, -1 if its
 argument is negative, and 0 if its argument is 0.  If the argument
 is a complex value, the imaginary component is ignored.
4 sin
?expressions functions sin
?functions sin
?sin
#sin(x) & radians & $\sin x$, sine of $x$ \\
%sin(x)@radians@$sin~x,$ sine of $x$
 The `sin` function returns the sine of its argument.  `sin` expects its
 argument to be in radians.
4 sinh
?expressions functions sinh
?functions sinh
?sinh
#sinh(x) & radians & $\sinh x$, hyperbolic sine $x$ \\
%sinh(x)@radians@$sinh~x,$ hyperbolic sine $x$
 The `sinh` function returns the hyperbolic sine of its argument.  `sinh`
 expects its argument to be in radians.
4 sqrt
?expressions functions sqrt
?functions sqrt
?sqrt
#sqrt(x) & any & $\sqrt{x}$,  square root of $x$ \\
%sqrt(x)@any@$sqrt x $, square root of $x$
 The `sqrt` function returns the square root of its argument.
4 tan
?expressions functions tan
?functions tan
?tan
#tan(x) & radians & $\tan x$,  tangent of $x$ \\
%tan(x)@radians@$tan~x,$ tangent of $x$
 The `tan` function returns the tangent of its argument.  `tan` expects
 its argument to be in radians.
4 tanh
?expressions functions tanh
?functions tanh
?tanh
#tanh(x) & radians & $\tanh x$, hyperbolic tangent of $x$\\
%tanh(x)@radians@$tanh~x,$ hyperbolic tangent of $x$
 The `tanh` function returns the hyperbolic tangent of its argument.
 `tanh` expects its argument to be in radians.
@end table
3 operators
?expressions operators
?operators
 The operators in 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.
4 binary
?expressions operators binary
?operators binary
?binary
 The following is a list of all the binary operators and their
 usages:

@start table - first is interactive cleartext form
  Symbol      Example      Explanation
   **          a**b          exponentiation
   *           a*b           multiplication
   /           a/b           division
   %           a%b         * modulo
   +           a+b           addition
   -           a-b           subtraction
   ==          a==b          equality
   !=          a!=b          inequality
   &           a&b         * bitwise AND
   ^           a^b         * bitwise exclusive OR
   |           a|b         * bitwise inclusive OR
   &&          a&&b        * logical AND
   ||          a||b        * logical OR
   ?:          a?b:c       * ternary operation
#\multicolumn{3}{|c|}{Binary Operators} \\
#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~ & * 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\\
#\verb~?:~ & \verb~a?b:c~ & * ternary operation\\
%Symbol@Example@Explanation
%_
%**@a**b@exponentiation
%*@a*b@multiplication
%/@a/b@division
%%@a%b@* modulo
%+@a+b@addition
%-@a-b@subtraction
%==@a==b@equality
%!=@a!=b@inequality
%&@a&b@* bitwise AND
%^@a^b@* bitwise exclusive OR
%|@a|b@* bitwise inclusive OR
%&&@a&&b@* logical AND
%||@a||b@* logical OR
%?:@a?b:c@* ternary operation

@end table
 (*) 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 && operand is not evaluated if the first is
 false; the second || operand is not evaluated if the first is true.

 The ternary operator evaluates its first argument (a).  If it is
 true (non-zero) the second argument (b) is evaluated and returned,
 otherwise the third argument (c) is evaluated and returned.
4 unary
?expressions operators unary
?operators unary
?unary
 The following is a list of all the unary operators and their
 usages:

@start table - first is interactive cleartext form
  Symbol     Example      Explanation
   -           -a          unary minus
   ~           ~a        * one's complement
   !           !a        * logical negation
   !           a!        * factorial
#\multicolumn{3}{|c|}{Unary Operators}\\
#Symbol & Example & Explanation \\ \hline
#\verb@-@ & \verb@-a@ & unary minus \\
#\verb@~@ & \verb@~a@ & * one's complement \\
#\verb@!@ & \verb@!a@ & * logical negation \\
#\verb@!@ & \verb@a!@ & * factorial \\
%-@-a@unary minus
%~@~a@* one's complement
%!@!a@* logical negation
%!@a!@*factorial

@end table
 (*) Starred explanations indicate that the operator requires an
 integer argument.

 The factorial operator returns a real number to allow a greater range.
2 help
?help
 The `help` command displays on-line help.  To specify information on a
 particular topic use the syntax:

     help <topic>

 If <topic> is not specified, a short message is printed about
 GNUPLOT. After help for the requested topic is given, help for
 a subtopic may be requested by typing its name, extending the help
 request. After that subtopic has been printed, you may extend the
 request again, as before, or go back one level to the previous topic,
 by simply pressing return without typing anything. Eventually, you
 will return to the GNUPLOT command line.
2 load
?load
 The `load` command executes each line of the specified input file as
 if it had been typed in interactively.  Files created by the `save`
 command can later be `load`ed.  Any text file containing valid
 commands can be created and then executed by the `load` command.
 Files being `load`ed may themselves contain `load` commands. See
 `comment` for information about comments in commands.

 The `load` command must be the last command on the line.

 Syntax:
         load <input-file>

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

 Examples:

         load 'work.gnu'
         load "func.dat"

 The `load` command is performed implicitly on any file names given as
 arguments to gnuplot. These are loaded in the order specified, and
 then gnuplot exits.
2 pause
?pause
 Pause is useful in conjunction with `load` files.  The command `pause`
 displays any text associated with the command and then waits the
 specified amount of time.  This allows one to build a `load` file
 and control the amount of time a finished graph is displayed.  The
 first argument is an expression that can be -1, 0, or a positive
 integer. Choosing -1 will wait until a carriage return is hit. Zero (0)
 won't pause at all, and a positive integer (such as 1 or 15) will
 wait the specified number of seconds.

 Note: Since pause is not part of the plot it may interact with
 different device drivers differently (depending upon how text and
 graphics are mixed).

 Examples:
         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."

 Syntax:
         pause <expression> {"string"}
 Note the string is optional, and if present must be enclosed in quotes.
2 plot
?plot
 `plot` is the primary command of the program.  It plots functions and
 data in many, many ways.  The full syntax of this command is:

   plot {ranges}  <function> {title} {style} {, <function> {title} {style}...}

 Where <function> is either a mathematical expression, the name of a
 data file enclosed in quotes, or a pair of mathematical expressions in
 the case of parametric functions.  User-defined functions and variables
 may also be defined here.

 Curly braces {,} denote optional items.

 A `plot` command can be as simple as

  plot sin(x)

 or as complex as (!)

  plot [t=1:10] [-pi:pi*2] tan(t),"data.1" with lines,t**2 with points
3 data-file
?plot datafile
?plot data-file
?datafile
?data-file
?data
 Discrete data contained in a file can displayed by specifying the
 name of the data file (enclosed in quotes) on the `plot` command
 line.

 Data files should contain one data point per line.  A data point may
 be specified either as an X and Y value separated by blank space, or
 as just the Y value, in which case the program will use the number
 of the coordinate as the X value.  Coordinate numbers start at 0
 and are incremented for each data point read.  To specify other
 formats, see `plot datafile using`.  Lines beginning with #
 (or ! on VMS) will be treated as comments and ignored.

 NOTE that blank lines cause a break in the input, and if the plot
 style is `lines` or `linespoints` (see `plot style`) there will be no
 line drawn between the preceding and following points. This does not
 change the plot style, as would plotting the data as separate curves.

 This example compares the data in the file population.dat to a
 theoretical curve:

         pop(x) = 103*exp((1965-x)/10)
         plot [1960:1990] 'population.dat', pop(x)

 The file population.dat might contain:

  # Gnu population in Antarctica since 1965
  1965   103
  1970   55
  1975   34
  1980   24
  1985   10
4 using
?plot datafile using
?plot data-file using
?using
 The format of data within a file can be selected with the `using`
 option.  The `xy` and `yx` specify the order of the `x` and `y`
 variables in the data file. To reverse the variables specify `yx`.
 To specify that the datafile should contain one variable specify `y`.

 Syntax:

         plot "datafile" { using { xy | yx | y } {"scanf string"} } ...

 If the `xy`, `yx` or `y` option is omitted, `xy` is used.
 If the scanf string is omitted, the default of `"%f%f"` is used.

 Examples:

         plot "MyData" using yx "%*f%f%*20[^\n]%f" with lines
 This causes data to be read from the file "MyData" using the format
 `yx "%*f%f%*20[^\n]%f"`.  The meaning of this format is: `%*f`
 ignore the first number, `%f` then read in the second and assign to y
 (the `yx` option of using), `%*20[^\n]` then ignore 20 non-newline
 characters, `%f` then read in the x value.

         plot "MyData" using "%f%f", "MyData" using "%f%*f%f"
 Causes gnuplot to plot the second and third columns of MyData versus
 the first column.

 Note: gnuplot first reads a line of the data file into a buffer and
 then does a
         sscanf(input_buffer, scanf_string, &x, &y);
 where `x` and `y` are of type `float`.  Any scanf string that specifies
 two `float` numbers may be used.
3 parametric
?plot parametric
?parametric
 When in parametric mode (`set parametric`) mathematical expressions must
 be given in pairs:
  plot sin(t),t**2

 Data files are plotted as before, except the parametric function
 must be fully specified before a data file is given as a plot.  In
 other words, the x parametric function (sin(t) above) and the y
 parametric function (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.

 Ranges take on a different meaning when in parametric mode.  The
 first specifiable range on the plot command is the trange, the
 next the xrange, and the last is the yrange.  The following plot
 shows setting the trange to [-pi:pi], the xrange to [-1.3:1.3]
 and the yrange to [-1:1] for the duration of the plot:
  plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2

 Other modifiers, such as `with` and `title` are required after
 the function has been fully specified:
  plot sin(t),t**2 with linespoints title 'Parametric example'
3 ranges
?plot ranges
?ranges
 The optional range specifies the region of the plot which will be displayed.

 Ranges may be provided on the `plot` command line and affect only
 that plot, or in the `set xrange` and `set yrange` commands, to
 change the default ranges for future plots.

 Syntax:
         [{dummy-var =} {xmin : xmax}] { [{ymin : ymax}] }

 Where dummy-var is the independent variable (the default is `x`,
 but this may be changed with the `set dummy` command) and the min
 and max terms can be expressions or constants.

 Both the min and max terms are optional.  The ':' is also optional
 if neither a min nor a max term is specified.  This allows '[]' to
 be used as a null range specification.

 Specifying a range in the `plot` command line turns autoscaling for
 that axis OFF for that plot. Using one of the `set` range commands
 turns autoscaling off for that axis for future plots, unless changed
 later. (See `set autoscale`).


 Examples:

 This uses current ranges:
         plot cos(x)

 This sets the xrange only:
         plot [-10:30] sin(pi*x)/(pi*x)

 This is the same, but uses t as the dummy-variable:
         plot [t = -10 :30]  sin(pi*t)/(pi*t)

 This sets both the x and yranges:
         plot [-pi:pi] [-3:3]  tan(x), 1/x

 This sets only the yrange:
         plot [] [-2:sin(5)*-8] sin(x)**besj0(x)

 This sets xmax and ymin only:
         plot [:200] [-pi:]  exp(sin(x))
3 style
?plot style
?style
 Plots may be displayed in one of four styles: `lines`, `points`,
 `linespoints`, `impulses`, or `dots`.  The `lines` style connects
 adjacent points with lines. The `points` style displays a small
 symbol at each point.  The `linespoints` style does both `lines` and
 `points`. The `impulses` style displays a vertical line from the X
 axis to each point. The `dots` style plots a tiny dot at each point;
 this is useful for scatter plots with many points.

 Default styles are chosen with the `set function style` and
 `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 than six are required.
 The LaTeX driver supplies an additional six point types (all variants
 of a circle), and thus will only repeat after twelve curves are
 plotted with points.

 If desired, the actual line type and point type used for a plot can
 be specified. Syntax:

         with <style> {<linetype> {<pointtype>}}

 Where <style> is either `lines`, `points`, `linespoints`, `impulses`,
 or `dots`. These keywords may be abbreviated.
 Curly braces denote optional items.  The <linetype> and <pointtype>
 are positive integers, and specify the line type and point type to
 be used for the plot.  Line type 1 is the first line type used by
 default, line type 2 is the second line type used by default etc.

 Examples:

 This plots sin(x) with impulses:
         plot sin(x) with impulses

 This plots sin(x) with points, cos(x) default:
         plot [-9:30]  sin(x) w points, cos(x)

 This plots tan(x) with the default function style, "data.1" with lines:
         plot [] [-2:5] tan(x), "data.1" with l

 This plots "leastsq.dat" with impulses:
         plot 'leastsq.dat' w i

 This plots sin(x) and cos(x) with the same line type:
         plot sin(x) with line 1, cos(x) with line 1

 This plots sin(x) and cos(x) with linespoints, using the
 same line type but different point types:
         plot sin(x) with linesp 1 3, cos(x) with linesp 1 4

 This plots file "data" with points style 3:
         plot "data" with points 1 3
 Note that the line style must be specified in order to specify the
 point style, even when it is irrelevant. Here the line style is 1 and
 the point style is 3, and the line style is irrelevant.
3 title
?plot title
 A title of each plot appears in the key.  By default the title is
 the function or file name as it appears on the plot command line.
 The title can be changed by using the `title` option. This option
 should precede any `with` option.

 Syntax:
         title <title>

 Where <title> is the new title of the plot and must be enclosed in
 quotes.

 Examples:

 This plots y=x with the title 'x':
         plot x

 This plots y=x with the title 'y=x':
         plot x title 'y=x'

 This plots x squared with title 'x^2' and "data.1" with title 'measured data':
         plot x**2 title "x^2", "data.1" t 'measured data'
2 print
?print
 The `print` command prints the value of <expression> to the screen.

 Syntax:
         print <expression>

 See `expressions`.
2 pwd
?pwd
 The `pwd` command prints the name of the working directory to the screen.

 Syntax:
         pwd
2 quit
?quit
 The `exit` and `quit` commands and your computer's END-OF-FILE
 character will exit GNUPLOT.  All these commands will clear the
 output device (as the `clear` command does) before exiting.
2 replot
?replot
 The `replot` command without arguments repeats the last `plot` command.
 This can be useful for viewing a plot with different `set` options,
 or when generating the same plot for several devices.

 Arguments specified after a `replot` command will be added onto the last
 `plot` command (with an implied ',' separator) before it is repeated.
 `replot` accepts the same arguments as the `plot` command except that
 ranges cannot be specified.
2 save
?save
 The `save` command saves user-defined functions, variables, set
 options or all three plus the last plot command to the specified file.

 Syntax:
         save  {<option>} <filename>

 Where <option> is `functions`, `variables` or `set`.  If no option is
 used GNUPLOT saves functions, variables, set options and the last plot
 command.

 `save`d files are written in text format and may be read by the `load`
 command.

 The filename must be enclosed in quotes.

 Examples:

         save "work.gnu"
         save functions 'func.dat'
         save var 'var.dat'
         save set "options.dat"
2 set-show
?set
?show
 The `set` command sets LOTS of options.

 The `show` command shows their settings.  `show all` shows all the
 settings.
3 arrow
?set arrow
?set noarrow
?show arrow
?arrow
?noarrow
 Arbitrary arrows can be placed on the plot using the `set arrow`
 command.

 Syntax:

          set arrow {tag} {from sx,sy} {to ex,ey}
          set noarrow {tag}
          show arrow


 Curly braces {} denote optional items.
 All positions x,y default to 0,0.
 The x and y values are in the graph's coordinate system.
 The tag is an integer that is used to identify 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 `set
 arrow` command with the appropriate tag, and specify the parts of the
 arrow to be changed.

 Arrows outside the plotted boundaries are permitted but may cause
 device errors; use at your own risk.

 Examples:

 To set an arrow pointing from the origin to (1,2) use
          set arrow to 1,2
 To set an arrow from (-10,4) to (-5,5), and tag the arrow number 3, use:
          set arrow 3 from -10,4 to -5,5
 To change the preceding arrow begin at 1,1, use
          set arrow 3 from 1,1
 To delete arrow number 2 use:
          set noarrow 2
 To delete all arrows use:
          set noarrow
 To show all arrows (in tag order) use:
          show arrow
3 autoscale
?set autoscale
?show autoscale
?autoscale
 Auto scaling may be set on the X and/or Y axis. The default is to
 autoscale both axes.

 If autoscaling of the Y axis is set, the Y axis is automatically scaled
 to fit the range of the function or data being plotted.  If autoscaling
 of the Y axis is not set, the current Y range is used.  See `set yrange`.

 If autoscaling of the X axis is set, the X axis is automatically scaled
 to fit the range of the data being plotted.  Autoscaling of the X axis
 will operate only on data.  Functions do not affect the X range and the
 range used for functions is determined by the data plots.
 See `set xrange`.

 Syntax:
         set autoscale <axes>
         set noautoscale <axes>
         show autoscale

 where <axes> is either `x`, `y`, or `xy`.
 If <axes> is not given then both axes are assumed.

 Examples:

 These set autoscaling of the Y axis.  X axis autoscaling not affected.
         set autoscale y

 This sets autoscaling of the X and Y axes.
         set autoscale xy
         set autoscale

 This disables autoscaling of the X and Y axes.
         set noautoscale

 This disables autoscaling of the X axis only.
         set noautoscale x
4 parametric mode
?autoscale parametric
?set autoscale t
 When in parametric mode (`set parametric`) the xrange is as
 fully scalable as the yrange.  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.

 When there is a mix of data files and functions, the xrange of
 the functions is selected as that of the data files if autoscale
 is true for X.  While this keeps the behavior compatible with
 non-parametric plotting, it may not be retained in the future.
 The problem is that, in parametric mode, the x and y ranges are
 not as distinguishable as in the non-parametric mode and this
 behavior may not be the most useful.

 For completeness sake a last command `set autoscale t` is accepted.
 However, the effect of this "scaling" is very minor.  When
 gnuplot determines that the t range would be empty it makes a
 small adjustment if autoscaling is true.  Otherwise, gnuplot
 gives an error.  Such behavior may, in fact, not be very useful
 and the command `set autoscale t` is certainly questionable.
3 clip
?set clip
?set noclip
?show clip
?clip
?noclip
 GNUPLOT can clip (actually, not plot at all) data points that fall
 within but too close to the boundaries (this is so the large symbols
 used for points will not extend outside the boundary lines).  To turn
 on clipping, use `set clip points`.  To turn it back off, use `set
 noclip points`. The default is `noclip`.  Without clipping you may have
 points near the boundaries that look bad; try adjusting the x and y ranges.

 Syntax:
         set clip points
         set noclip points

 GNUPLOT can also clip lines that connect a point that is in range
 with a point that is out of range. The default is to draw the
 in-range portion of such lines (i.e., to "clip" them). With the
 following syntax, the default is `set clip one`. The alternative
 (`set noclip one`) is to not draw any portion of the line segment. In
 no case is a line drawn outside the plotting area.

 Syntax:
         set clip one
         set noclip one

 GNUPLOT does not show lines that are wholly out of range. Some lines
 may have both endpoints out of range, but pass through the plotting
 area. By default, GNUPLOT does not draw these lines (`set noclip
 two`). They may be drawn (and clipped) with `set clip two`.

 Syntax:
         set clip two
         set noclip two

 To check the state of all forms of clipping, use
         show clip

 The following forms are also permitted. These allow backward
 compatibility with older versions.
        set clip
        set noclip
 `set clip` is synonymous with `set clip points`. `set noclip` turns
 off all three types of clipping (`points`, `one`, and `two`).
3 dummy
?set dummy
?show dummy
?dummy
 By default, GNUPLOT assumes that the independent variable for
 the `plot` command line is `x`.  `x` is called the dummy variable because
 it is just a notation to indicate the independent variable.  The
 `set dummy` command changes this default dummy variable name.  For
 example, you may find it more convenient to call the dummy variable
 `t` when plotting time functions:

         set dummy t
         plot sin(t), cos(t)

 Syntax:
         set dummy <dummy-var>
         show dummy
3 format
?set format
?show format
?format
 The format of the tic-mark labels can be set with the `set format`
 command.  The default format for both axes is "%g", but other formats
 such as "%.2f" or "%3.0fm" are often desirable.  Anything accepted by
 printf when given a double precision number, and then accepted by the
 terminal, will work.  In particular, the formats f, e, and g will work,
 and the d, o, x, c, s, and u formats will not work.

 Syntax:
         set format {<axes>} {"format-string"}
         show format

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

 See also `set xtics` and `set ytics` for more control over tic labels.
3 functions
?show functions
 The `show functions` command lists all user-defined functions and
 their definitions.

 Syntax:
         show functions
3 grid
?set grid
?show grid
?grid
 The optional `set grid` draws a grid at the tic marks with the axis
 linetype.

 Syntax:
         set grid
         set nogrid
         show grid
3 key
?set key
?show key
?key
 The `set key` enables a key describing curves on a plot.
 By default the key is placed in the upper right corner of
 the plot.

 Syntax:
         set key
         set key x,y
         set nokey
         show key

 The coordinates x,y specify the location of the key on the plot.
 The key is drawn as a sequence of lines, with one plot described
 on each line.  On the right hand side of each line is a
 representation that attempts to mimic the way the curve is plotted.
 On the left side of each line is the text description,
 obtained from the `plot` command.  The lines are vertically
 arranged so an imaginary straight line divides the left- and
 right-hand sides of the key.  It is the x-coordinate of this
 line that you specify with the optional x in the `set key`
 command; the y in the `set key` command is top of the key.
 Some or all of the key may be outside of the plot boundary, if you
 wish, although this may interfere with other labels and may cause an
 error on some devices.

 Examples:

 This places the key at the default location:
         set key
 This disables the key.
         set nokey
 This places a key at coordinates 2,3.5
         set key 2,3.5
3 label
?set label
?set nolabel
?show label
?label
?nolabel
 Arbitrary labels can be placed on the plot using the `set label`
 command.

 Syntax:

          set label {tag} {"label_text"} {at x,y} {<justification>}
          set nolabel {tag}
          show label


 Curly braces {} denote optional items.
 The text defaults to "", and the position x,y to 0,0.
 The x and y values are in the graph's coordinate system.
 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 change a specific
 label. To change any attribute of an existing label, use the `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 point x,y. If you
 want to adjust the way the label is positioned with respect to the
 point x,y, add the parameter <justification>, which may be `left`,
 `right` or `center`, indicating that the point is to be at the left,
 right or center of the text.  The <justification> may be abbreviated.
 Labels outside the plotted boundaries are permitted but may interfere
 with axes labels or other text; use at your own risk.

 Examples:

 To set a label at (1,2) to "y=x" use:
          set label "y=x" at 1,2
 To set a label "y=x^2" with the right of the text at (2,3), and tag
 the label number 3, use:
          set label 3 "y=x^2" at 2,3 right
 To change the preceding label to center justification, use:
          set label 3 center
 To delete label number 2 use:
          set nolabel 2
 To delete all labels use:
          set nolabel
 To show all labels (in tag order) use:
          show label

 The Imagen driver allows \\ in a string to specify a newline.
3 logscale
?set logscale
?set nologscale
?show logscale
?logscale
?nologscale
 Log scaling may be set on the X and/or Y axis.

 Syntax:
         set logscale <axes>
         set nologscale <axes>
         show logscale

 Where <axes> is either `x`, `y`, or `xy`.
 If <axes> is not given then both axes are assumed.
 The command `set logscale` turns on log scaling on the specified
 axes, while `set nologscale` turns off log scaling.
3 offsets
?set offsets
?show offsets
?offsets
 The amount of the graph that the plot takes up may be controlled
 to some extent with the `set offsets` command.  This command takes
 four offset arguments -- <left>, <right>, <top> and <bottom>.
 By default, each offset is 0.  Each offest may be a constant or
 an expression.  Left and right offsets are given in units of
 the x axis, while top and bottom offsets are given in units of
 the y axis.  The plot of sin(x), displayed with offsets of
 0, 0, 2, 2 will take up  1/3 of the displayed y axis.
 Offsets are particularly useful with polar coordinates as a means
 of compensating for aspect ratio distortion.

 Syntax:
         set offsets <left>, <right>, <top>, <bottom>
         show offsets
3 output
?set output
?show output
?output
 By default, plots are displayed to the standard output.  The
 `set output` command redirects the display to the specified file or
 device.

 Syntax:
         set output {<filename>}
         show output

 The filename must be enclosed in quotes.  If the filename is
 omitted, output will be sent to the standard output.
3 parametric
?set parametric
?show parametric
?parametric
 The `set parametric` command changes the meaning of the plot from
 normal functions to parametric functions.  The command
 `set noparametric` changes the plotting style back to normal,
 single-valued expression plotting.

 Parametric functions are determined by a pair of functions
 operating on a `parameter`, such as sin(t),cos(t) (which describes
 a circle if `t` ranges over [-pi:pi]).  Hence it takes two
 parametric function specifications in terms of the parametric
 dummy argument to describe a single graph.

 The total set of possible plots is a superset of the simple f(x)
 style plots, since the two functions can describe both 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) since
 the x values are computed with just the identity function.  Note
 that the order the parametric function is specified is xfunction,
 yfunction and that each operates over the common parametric domain.

 Also, the `set parametric` function implies a new range of values.
 Whereas the normal f(x) style plotting assumes an xrange and yrange,
 the parametric mode additionally specifies a trange.  The trange
 may be specified directly with `set trange`, by specifying the
 range on the plot command, or indirectly with `set autoscale t`.
3 polar
?set polar
?show polar
?polar
 The `set polar` command changes the meaning of the plot from
 rectangular coordinates to polar coordinates.  In polar
 coordinates, the dummy variable (x) is an angle.  The range
 of this angle is changed from whatever it was to [0:2*pi].

 The command `set nopolar` changes the meaning of the plot back
 to the default rectangular coordinate system.  The range of
 x is changed from whatever it was to [-10:10].

 While in polar coordinates the meaning of an expression in x
 is really r = f(x), where x is an angle of rotation. The xrange
 controls the domain (the angle) of the function, and the yrange
 controls the range (the radius). The plot is plotted on a rectangular
 grid, and the `x` and `y` axes are both in units of the radius. Thus,
 the yrange controls both dimensions of the plot output. There is no
 way to specify the output dimensions separately.

 Syntax:
         set polar
         set nopolar
         show polar
 Example:
         set polar
         plot x*sin(x)
         plot [-2*pi:2*pi] [-3:3] x*sin(x)
 The first plot uses the default polar angular domain of 0 to 2*pi.
 The radius (and the size of the plot) is scaled automatically. The
 second plot expands the domain, and restricts the range of the radius
 (and the size of the plot) to [-3:3].
3 samples
?set samples
?show samples
?samples
 The sampling rate of functions may be changed by the `set samples`
 command.  By default, sampling is set to 160 points.  A higher
 sampling rate will produce more accurate plots, but will take
 longer.  When plotting datafiles, the sampling rate must be set
 higher than the number of data points.

 Syntax:
         set samples <expression>
         show samples
3 size
?set size
?show size
?size
 The `set size` command scales the displayed size of the plot.
 On some terminals, changing the size of the plot will result in
 text being misplaced.  Increasing the size of the plot may
 produce strange results.  Decreasing is safer.

 Syntax:

         set size {x,y}
         show size

 The x and y values are the scaling factors for the size.
 The defaults (1,1) are selected if the scaling factors are omitted.

 Examples:

 To set the size to normal size use:
         set size
 To make the plot half size use:
         set size 0.5,0.5
 To show the size use:
         show size

 For the LaTeX and Fig terminals the default size (scale factor 1,1)
 is 5 inches wide by 3 inches high. Note that the size of the plot
 includes the space used by the labels; the plotting area itself is
 smaller.
3 style
?set style
?show style
?style
 Plots may be displayed in one of five styles: `lines`, `points`,
 `linespoints`, `impulses`, or `dots`.  The `lines` style connects
 adjacent points with lines. The `points` style displays a small
 symbol at each point.  The `linespoints` style does both `lines` and
 `points`. The `impulses` style displays a vertical line from the X
 axis to each point. The `dots` style plots a tiny dot at each data
 point; this is useful for scatter plots with many points.

 Default styles are chosen with the `set function style` and `set
 data style` commands.  See `plot style` for information about how
 to override the default plotting style for individual functions.

 Syntax:
         set function style <style>
         set data style <style>
         show function style
         show data style

 Where <style> is either `lines`, `points`, `linespoints`, `impulses`,
 or `dots`.
3 terminal
?set terminal
?show terminal
?terminal
 GNUPLOT supports many different graphics devices.  Use the `set
 terminal` command to select the type of device for which GNUPLOT
 will produce output.

 Syntax:
         set terminal {<terminal-type>}
         show terminal

 If <terminal-type> is omitted, GNUPLOT will list the available
 terminal types.  <terminal-type> may be abbreviated.

 Use `set output` to redirect this output to a file or device.
3 tics
?set tics
?show tics
?tics
 By default, tics are drawn inwards from the border on all four sides.
 The `set tics` command can be used to change the tics to be
 drawn outwards on the left and bottom borders only.
 This is useful when doing impulse plots.

 Syntax:
         set tics {<direction>}
         show tics

 Where <direction> may be `in`, `out` or nothing (which is the same as in).

 See also the `set xtics` and `set ytics` command for more control of
 tic marks.
3 title
?set title
?show title
?title
 The `set title` command sets the title which will be centered
 at the top of the plot.

 Syntax:
          set title
          set title "title-text"
          show title

 The first clears the title (default).
 The second form sets the title to "title-text" (without the quotes).

 The Imagen driver allows \\ in a string to specify a newline.
3 trange
?set trange
?show trange
?trange
 The `set trange` command sets the parametric range used to compute
 x and y values when in parametric mode.  If not in parametric mode
 (see `set parametric`) then this range is not used.  This command
 does not affect XY autoscaling or XY ranges.

 This range may also be specified on the `plot` command line when
 in parametric mode.

 Syntax:
         set trange [{<tmin> : <tmax>}]

 Where <tmin> and <tmax> terms are expressions or constants.

 Both the <tmin> and <tmax> terms are optional. Anything omitted will
 not be changed, so
         set trange [:10]
 changes tmax to 10 without affecting tmin.
3 xtics
3 variables
?show variables
 The `show variables` command lists all user-defined variables and
 their values.

 Syntax:
         show variables
3 xlabel
?set xlabel
?show xlabel
?xlabel
 The `set xlabel` command sets the x-axis label which will be centered
 at the bottom of the plot.

 Syntax:
          set xlabel
          set xlabel "label"
          show xlabel

 The first clears the x-axis label (default).
 The second form sets the x-axis label to "label" (without the quotes).

 The Imagen driver allows \\ in a string to specify a newline.
3 xrange
?set xrange
?show xrange
?xrange
 The `set xrange` command sets the horizontal range which will be
 displayed.  This command turns X axis autoscaling OFF.

 This range may also be specified on the `plot` command line.

 Syntax:
         set xrange [{<xmin> : <xmax>}]

 Where <xmin> and <xmax> terms are expressions or constants.

 Both the <xmin> and <xmax> terms are optional. Anything omitted will
 not be changed, so
         set xrange [:10]
 changes xmax to 10 without affecting xmin.
3 xtics
?set xtics
?set noxtics
?show xtics
?xtics
?noxtics
 Very fine control of the `x` axes tic marks is possible with the `set
 xtics` and `set noxtics` command. The x-axis tic marks may be turned
 off with the `set noxtics` command. They may be turned on (the
 default state) with `set xtics`.

 If you prefer your own series of tic marks, you may use the form
          set xtics <start>, <incr>{, <end>}
 The curly braces indicate that the <end> parameter is optional.
 This command specifies that a series of tics will be plotted on the
 `x` axis between the `x` 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. Example:
           set xtics 0,.5,10
 makes tics 0, 0.5, 1, 1.5, ..., 9.5, 10.

 If you need arbitrary tic positions, or non-numeric tic labels,
 any non-empty set of tic positions and labels may be given with this
 format:
          set xtics ({"label"} pos {, {"label"} pos}...)
 Again curly braces contain optional components. Thus, a set of tics
 are a set of positions, each with its own optional label. Note that
 the label is a string enclosed by quotes, and may be a constant
 string, such as "hello", or contain formatting information for the tic
 number (which is the same as the position), such as "%3f clients".
 See `set format` for more information about this case. The label may
 even be empty. Examples:
          set xtics ("low" 0, "medium" 50, "high" 100)
          set xtics (1,2,4,8,16,32,64,128,256,512,1024)
          set xtics ("bottom" 0, "" 10, "top" 20)

 Tics will only be plotted when in range.

 The `set ytics` and `set noytics` commands work identically.
 See also `set format` command.
3 xzeroaxis
?set xzeroaxis
?show xzeroaxis
?xzeroaxis
 `set xzeroaxis` draws the x-axis.  By default, this option is on.
 `set noxzeroaxis` causes gnuplot to omit the x-axis.

 Syntax:
         set xzeroaxis
         set noxzeroaxis
         show xzeroaxis
3 yzeroaxis
?set yzeroaxis
?show yzeroaxis
?yzeroaxis
 `set yzeroaxis` draws the y-axis.  By default, this option is on.
 `set noyzeroaxis` causes gnuplot to omit the y-axis.

 Syntax:
         set yzeroaxis
         set noyzeroaxis
         show yzeroaxis
3 ylabel
?set ylabel
?show ylabel
?ylabel
 The `set ylabel` command sets the y-axis label.
 The position of this 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.

 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 Latex and EEPIC drivers use this method.  The user must insert
 line breaks using \\ to prevent the ylabel from overwriting
 the plot.  To produce a vertical row of characters, add \\
 between every printing character.

 Syntax:
          set ylabel
          set ylabel "label"
          show ylabel

 The first clears the y-axis label (default).
 The second form sets the y-axis label to "label" (without the quotes).

 The Latex, EEPIC, and Imagen drivers allow \\ in a string to specify
 a newline.
3 yrange
?set yrange
?show yrange
?yrange
 The `set yrange` command sets the vertical range which will be
 displayed.  This command turns Y axis autoscaling OFF.

 This range may also be specified on the `plot` command line.

 Syntax:
         set yrange [{<ymin> : <ymax>}]

 Where <ymin> and <ymax> terms are expressions or constants.

 Both the <ymin> and <ymax> terms are optional. Anything omitted will
 not be changed, so
         set yrange [:10]
 changes ymax to 10 without affecting ymin.
3 ytics
?set ytics
?set noytics
?show ytics
?ytics
?noytics
 The `set ytics` and `set noytics` commands are similar to the `set xtics`
 and `set noxtics` commands. Please see `set xtics`.
3 zero
?set zero
?show zero
?zero
 GNUPLOT will not plot a point if its imaginary part is greater in
 magnitude than the `zero` threshold.  The default `zero` value is
 1e-8. This can be changed with the `set zero` command.

 Syntax:
         set zero <expression>
         show zero
3 zeroaxis
?set zeroaxis
?show zeroaxis
?zeroaxis
 `set zeroaxis` draws the x-axis and y-axis.  By default, this option is on.
 `set noxzeroaxis` causes gnuplot to omit the axes.

 Syntax:
         set zeroaxis
         set nozeroaxis
         show zeroaxis
 See `set xzeroaxis` and `set yzeroaxis`.
2 shell
?shell
 The `shell` command spawns an interactive shell.  To return to
 GNUPLOT, type `logout` if using VMS, `exit` or your END-OF-FILE
 character if using Unix, or `exit` if using MS-DOS.

 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 GNUPLOT after this command is
 executed.  For example,

      ! dir

 prints a directory listing and then returns to GNUPLOT.
2 start-up
?startup
?start
?.gnuplot
 When GNUPLOT is run, it looks for an initialization file to load.
 This file is called `.gnuplot` on Unix systems, and `GNUPLOT.INI` on
 other systems.  If this file is not found in the current directory,
 the program will look for it in your home directory (under MS-DOS, the
 environment variable GNUPLOT should contain the name of this
 directory).

 If this file is found, GNUPLOT executes the commands in this file.
 This is most useful for setting your terminal type and defining any
 functions or variables which you use often.  The variable `pi` is
 already defined for you.
2 substitution
?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.

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

 Command-line substitution can be used anywhere on the GNUPLOT command
 line.


 Example:

 This will run the program `leastsq` and substitute `leastsq`
 (including quotes) on the command line with its output:

  f(x) = `leastsq`

 or, in VMS

  f(x) = `run leastsq`
2 user-defined
?userdefined
?variables
 You may define your own functions and variables.  User-defined
 functions and variables may be used anywhere.

 User-defined function syntax:
     <function-name> ( <dummy-var> ) =  <expression>

 Where <expression> is defined in terms of <dummy-var>.

 User-defined variable syntax:
     <variable-name> = <constant-expression>

 Examples:
     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

 The variable `pi` is already defined for you.

 See `show functions` and `show variables`.
2 bugs
?bugs
 The atan() function does not work correctly for complex arguments.

 The bessel functions do not work for complex arguments.

 The most important known bug is actually in the stdio library for the
 Sun4 operating system (SunOS Sys4-3.2). The "%g" format for `printf`
 sometimes incorrectly prints numbers (e.g., 200000.0 as "2").  Thus,
 tic mark labels may be incorrect on a Sun4 version of gnuplot.  You
 may work around it by rescaling your data or by using the `set format`
 command to change the tic mark format to "%7.0f" 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 "00 12" with
 the format "%f %f" and reads 0 and 0 instead of 0 and 12.  This
 affects data input. If your data file contains X coordinates that are
 zero but are specified like '00', '000', etc, then you will read the
 wrong Y values. Check your data files or do not use a Sun4 until they
 fix the bug. It does NOT appear that this has been fixed in SunOS 4.0.

 Microsoft C 5.1 has a nasty bug associated with the %g format for
 printf.  When any of the formats "%.2g", "%.1g", "%.0g", "%.g" 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.

 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.
 Gnuplot compiled with Turbo 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.

 Please report any bugs you find to pixar![e-mail] or
 pixar![e-mail].