[ubuntu-uk] process control charts! Chart software

[Thomas Ibbotson]

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javadayaz wrote:
> looks like it is command line based. so probably not for me then ! :(
> 

Don't be so scared of the command line, it's not so hard to learn to use
gnuplot. If you didn't know how to use a GUI application you would have
to spend some time learning, the only difference being with a GUI you
can guess which buttons to press.

So to get you started:
To start gnuplot, just type "gnuplot" at a terminal, then you'll get a
prompt looking something like this:

	G N U P L O T
	Version 4.2 patchlevel 3
	last modified Mar 2008
	System: Linux 2.6.27-11-generic

	Copyright (C) 1986 - 1993, 1998, 2004, 2007, 2008
	Thomas Williams, Colin Kelley and many others

	Type `help` to access the on-line reference manual.
	The gnuplot FAQ is available from http://www.gnuplot.info/faq/

	Send bug reports and suggestions to
<http://sourceforge.net/projects/gnuplot>


Terminal type set to 'wxt'
gnuplot>

To plot a graph of sin(x) here's what you'd type:
gnuplot> plot sin(x)

and a graph of sin(x) should pop up in a window.

If you have a file with data in it, as long as they are in columns
gnuplot can plot them easily for you:
gnuplot>plot "data.txt"

where data.txt looks something like:
1  1
2  4
3  9
4  16
5  25

If you have more than one column, you use the "using" modifier i.e.
gnuplot> plot "data.txt" using 1:3

which tells gnuplot to plot columns 1 and 3 from the data.txt file.

The other important thing to know is how to write something to a file.
First you need to decide what type of file you would like to output,
such as "png" or "postscript". So here are the commands you would type:

gnuplot> set terminal png
[This sets the file to be of type "png"]
gnuplot> set output "mygraph.png"
[This opens the file for writing to it]
gnuplot> plot "data.txt"
[This plots the graph and puts the output into the file]
gnuplot> unset output
[This closes the file]

This is all just straight off the top of my head, so it's really not
hard to use once you've played with it a bit. There's plenty of good
information on the web for using gnuplot, but if you find yourself
stuck, don't hesitate to ask. As you might have noticed I quite like
gnuplot and would be willing to help...

Of course you can always type "help" at the gnuplot command line for
some interactive help.

gnuplot> help

Tom
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