View Source: GnuPlot - Waikato Linux Users Group

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The old-school Unix way of generating graphs from numeric data. It has very verbose documentation, but unfortunately it lacks in practical examples.

!!!Hints
!! Output format
By default, gnuplot creates [X11] windows and draws the graphs to your [XServer]. But that's no good for embedding it into a report, so do:
<verbatim>
set output "filename.ps"
set term postscript color
[...]
plot [your plot command]
</verbatim>

If you use [LaTeX], you can get gnuplot to output a LaTeX picture instead of embedding a graphic in your report:
<verbatim>
set output "foo.tex"
set term latex
[...]
plot [your plot command]
</verbatim>
Note that your latex file should "\usepackage{latexsym}" so that it knows about several shapes that gnuplot outputs (such as \Diamond and \Box). Try "help set term latex" for more info.

!!Vertical Lines
The default is to give a function that calculates "y" for various values of "x", but that makes it difficult to get a vertical line. Do
<verbatim>
set parametric
# vertical line
plot 0, t
# horizontal
plot t, 0
# or just plain old
plot 5
</verbatim>


!!Multiple columns from the same data file
<verbatim>
set pointsize 2
# plot [xrange] [yrange] function, function, ....
# do columns 3,4 and 6, using the first column for x
plot [0:2] [0:100] "input" using 1:3 with linespoints title "3rd", \
  "input" u 1:4 w lp t "4th", "input" u 1:6 w lp t "6th"
</verbatim>
As you see, command names can be shortened, which can
make it hard to understand what is happening :)

!!Multiple plots on a single page
Say you want to put 2 graphs on a single A4 bit of paper to print it out
<verbatim>
set terminal postscript portrait
set size 1,1 # The documentation recommends you set to full size first
set origin 0,0
set output "output.ps"
set multiplot # Enter multiplot mode. Your prompt will become 'multiplot>'
set size 1,0.5
set origin 0,0
plot "input" using 1:2 with lines
set size 1,0.5
set origin 0,0.5
plot "input" using 1:3 with lines
unset multiplot # Exit multiplot mode
</verbatim>

!! Plotting timeseries data
<verbatim>
set xdata time
set timefmt "%H:%M:%S"
set xrange ["8:00:00":"18:00:00"]
</verbatim>
Timestamps in your data file will now be recognised.  Gaps in your time data will show up as gaps in the graph.

!! Normal distribution
Define the following:
<verbatim>
invsqrt2pi=1.0/sqrt(2.0*pi)
normal(x,mu,sigma)=invsqrt2pi/sigma*exp(-0.5*((x-mu)/sigma)**2)
</verbatim>
Now, if you want a normal distribution with mean 13 and SD 1, you can go
<verbatim>
plot normal(x,13,1)
</verbatim>

!! Force a scale
<verbatim>
set xrange[0:10]
set yrange[50:100]
</verbatim>
One page links to GnuPlot:
PerlOneLiners
Last edited on Tuesday, June 12, 2007 4:04:44 pm by AlastairPorter
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