GnuPlot is the ultimate plotting tool and very powerful which has the downside of being quite hard to use especially for new users. Hopefully this article clears things up a bit (for me at least).

Probably the most common task performed when using a plotting tool is … plotting! Here are a few examples:

Plotting a function:

gnuplot> plot f(x) = x**2, f(x)

The same as above, but giving the range to plot:

gnuplot> plot [-5:5] f(x) = x**2, f(x)

Plotting two functions in the same plot:

gnuplot> plot f(x) = x**2, g(x) = x**3, f(x), g(x)

First, generate some data:

$ ping nwl.cc | sed -un 's/.*time=\(.*\) ms/\1/p' >/tmp/data

The output looks like this:

20.8
20.7
23.2
20.2
21.0
19.3
21.2
20.9
22.6
...

Now plot it:

gnuplot> plot '/tmp/data' with lines

File output is configured by setting a different terminal than the default x11 for the file type to generate and setting the output variable for the filename:

gnuplot> set terminal png size 800,600
gnuplot> set output '/tmp/data.png'

Afterwards the output of any plot command will be written to /tmp/data.png in png format.

Creating PDFs works equvalently, but the size parameter is interpreted differently (inches instead of pixels):

gnuplot> set terminal pdf size 8,6
gnuplot> set output '/tmp/data.pdf'

But it gets even better, latex output:

gnuplot> set terminal latex size 8,6
gnuplot> set output '/tmp/data.tex'

There are various output formats available, one may even chose between different latex packages to use. For reference, see the output of set terminal without further parameters.