Tony's Quick Gnuplot Guide

$Id: gnuplot.html,v 1.2 1998/02/24 08:39:19 tdarugar Exp $
http://www.parand.com/docs/gnuplot.html

This is a very short guide to using gnuplot. Just the basics.

The format of the data is very simple. All gnuplot wants is a text file with 2 numbers per line: the first is the x value, the second the y value. For example, it'll happily plot this:

So, make your data look like that. Now for the gnuplot part: start it up with

	gnuplot

The main commands you'll care about:

help
The help facility is actually quite good.
quit
plot "filename"
Plots the data from the file filename.
plot "filename1", "filename2"
Plots the data from the file filename1 and filename2 on the same graph.
set data style XXX
where XXX is one of 'lines', 'points', 'linespoints', 'dots', 'impulses', or 'errorbars' This sets the way the data will be plotted. linespoints is a nice one.
cd "dirName"
Change directory, to where your data is, for example. Note that if you print things, etc, the output goes into this directory.
set title "Grand old Title"
set xlabel "Guess what"
set ylabel "..."
set terminal XXX
This command lets you specify what format you want the output to be in. It could be "x11" to send data to the screen, or "postscript" to produce output as postscript, and so forth.

So now you're plotting your beautiful data, and want a printout. Do this:

set output "output.ps"
set terminal postscript default
[your plotting commands]
show output
set terminal x11

Substituting your favorite filenames as appropriate. You'll get a postscript file. So, one last trick: you can put all these commands into a text file, and run it from within gnuplot with

load "scriptfile"

Or, you can give it as a commandline parameter to gnuplot, as in

gnuplot scriptfile

Examples

set term pbm small color
set size 0.8,0.8
set output "/tmp/nSubs.pbm"
set title "Number of Subscribers Per Day"
set xlabel "Date"
set ylabel "Number of Subscribers"
plot "< tail -30 /usr/local/etc/mc-httpd9/stats/dates.txt" using 1:3 title 'Number of Subscribers' with boxes
show output

Good luck. Tony. (tdarugar@binevolve.com)