ARM Club 3/TheARMClub_PDCD3.iso/hensa/maths/graphdraw_1/!GraphDraw_Resources_EditHelp

Text File | 1995-04-22 | 8.4 KB | 307 lines

Information is available on:


  What This Software Does

  Entering Data

  The Graphdraw Edit Window Menu

  Graph Window Menus

  Further Information


  WIMP Key Presses
________________________________________

Note that if any read me files are
supplied as part of this application,
they may have more recent information
than is contained in this file.

GraphDraw is © Chris Johnson, 1992
________________________________________

This application provides interactive
help when the !Help application is
active.
________________________________________


What This Software Does

It allows the entry of the x and y
values for a number of data, and the
data may then be fit to

a. best straight line
b. best parabola
c. a cubic spline curve
d. a polynomial of order up to 6

A number of options for obtaining
various forms of hard copy exist
(saving as a !Draw file, or printing via
any standard RISC-OS printer driver).

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Entering Data

Clicking SELECT on the iconbar icon will
open an empty edit window, into which
the pairs of x,y data may be entered.
This version allows a maximum of 200
data point pairs.

Full scrolling and editing facilities
are available during data entry, by
means of the arrow keys, either alone or
in conjunction with SHIFT or CTRL. Page
up/down are the same as SHIFT+arrow. One
useful key combination is
CTRL+SHIFT+COPY, which will delete the
data point at the cursor and close up
the rest of the data.

The function key f3 will bring up the
standard save as dialogue box (this is
provided also as a menu choice).

Double clicking on a GraphDraw data file
or dragging a data file either into the
edit window, or to the iconbar icon will
load the data, overwriting any data that
had previously been entered.

Besides files in GraphDraw format, files
of file type text, data or CSV can be
loaded by dragging into the edit window
or onto the iconbar icon. In some cases,
if the file does not start with the
standard graphdraw header, a query
window will open for confirmation before
loading the file.

Data can also be passed in either
direction between the GraphDraw edit
window and a !edit window. Thus editing
can be carried out using the !edit
application if preferred. Data can be
entered 'from scratch' using !edit, and
then transferred to the !GraphDraw
application (by dragging a save icon to
its edit window or its iconbar icon), as
long as the !GraphDraw application can
recognise a valid data file. This
version of !GraphDraw now supports
direct RAM transfer for all its loading
and saving operations.

As the graphdraw application will deal
with files of comma separated ASCII data
it is possible to set up other
applications to produce data files of
the correct form.


Error Bars
If the Error bars icon at the bottom of
the edit window is selected by clicking
on it, the edit window will be extended,
allowing access to two further columns
of data. These are for use in entering
error limits to the points. The minimum
y limit and maximum y limit for each
point may be entered. When the graph is
plotted, the error bars corresponding to
these limits will be plotted.

In some cases it may be sufficient to
use a constant fraction for the error
bars. This may be done very simply by
entering the percentage error, e.g. 10,
into the writable icon, and then
clicking on the "Calc constant %" icon.
The calculated values will then be
written into the tables of data.

If the error bars icon is deselected,
the edit window will contract to the
normal size, and the error bars will not
be plotted. The data is retained, and
may be plotted again by reselecting the
error bars icon.
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The GraphDraw Edit Window Menu

All of the data processing and data
display facilities are accessed from the
edit window menu.

Clicking the 'menu' button in the edit
window brings up the following choices.


Clear data
 This will irretrievably clear the
current data prior to the entry of new
data. Graphdraw asks for confirmation
before clearing the data.


Save file
 Data files may be saved by dragging the
save icon to a directory viewer. If the
full path name is set up, then you can
also click on the OK icon to save the
data.

The function key F3 can be used as a
short cut for this option (unless the
graph window is open, when F3 will bring
up the "save drawfile" dialogue box).

It is also possible to drag the save
icon to a !Edit window, or to the !Edit
icon on the iconbar. The data is then
transferred into !Edit.


Plot points
 This will simply plot a scaled graph of
the data. Additional sub-menu choices
allow you to plot the data as is, as
semi-log x, semi-log y or as a log-log
plot.


Join points
 This plots the points and joins each
point to the next with a straight line.
The log plotting options are available
as above.


Best line
 This will carry out a standard linear
regression by the least squares method
to calculate the best fit straight line
through the data. A window will open
displaying the slope, intercept on y
axis, correlation coefficient and the
standard errors of the slope and
intercept. Clicking 'menu' in this
window allows the following choices.

   Graph
   -----
   This will display a graph of the data
points with the calculated best line
superimposed. Clicking 'menu' in the
graph window then leads to a further set
of options.

   Print data
   ----------
   This will send the results of the
calculation to any printer connected to
the computer. The individual errors
calculated for each data point are also
printed.


Parabola
 This will carry out a least squares fit
of the data to the equation of a
parabola

      y = u + vX + wX^2.

This is a useful technique for fitting
data to a simple curve. A window will
open showing the calculated values of
the coefficients u, v and w. Clicking
'menu' in this window will bring up the
same two options as described above,
i.e. graph and Print data.


Polynomial
 This will carry out a standard
polynomial fit for orders 3 to 6. Some
of the higher order options may be
greyed out if there are not enough data
points. Selecting a particular order
will force the program to calculate that
specific order polynomial, whereas if
'All' is selected, the program will try
all possible orders (3 to 6) and report
the one which gives the smallest
deviation. A window will open showing
the results of the calculation, and
clicking 'menu' on this window leads to
the same options as above.


Cubic spline
 This option leads to a small dialogue
box, which at present simply requests
the 'fit factor' to be specified. This
value must lie BETWEEN 0 and 1. In
theory, a value of 0 will plot a
straight line through the points, while
a value of 1 will force the curve
through every point. In practice these
values cannot be used, since a divide by
zero error is generated during certain
matrix inversion operations. Little is
lost since a value of 0.9999 or 0.0001
will give essentially the same result as
1 or 0. Curve fitting is always very
subjective, and it is up to the user to
decide the degree of smoothing
acceptable for any particular set of
data. A value of 0.5 is an obvious
starting point for any data known to
have scatter or experimental error.

Once <return> is pressed, the spline
plot will be displayed. For this plot,
it requires all the data to be sorted in
order. The program automatically sorts
the data in ascending order of x values
before carrying out the spline routine.
Note that this sorting occurs whenever
any of the plotting routines are used.


Transform X
 Allows the x data to be transformed in
a number of standard ways, e.g. LOG,
reciprocal. These operations are
cumulative, but it is up to the user to
remember the sequence of
transformations. Only the last
transformation can be "undone".


Transform Y
 As for transform X but on the y data.


Swap X and Y
 Simply interchanges the x and y data
pairs.
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Graph Window Menus

Whenever a graph is being displayed,
clicking 'menu' will lead to a further
range of options.
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Further Information

Help windows with appropriate text are
also available from the Iconbar menu,
and from the graph window menu.
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WIMP Key Presses

Function key F1 attempts to start up
either !Help or !BubbleHelp.

Function key F3 brings up a "save as"
dialogue box for saving the data (or the
graph as a draw file, depending on
whether a graph is being displayed at
the time).
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