It is recommended that you write the results of your program to a file, then plot those results separately. This means you can play with the presentation of your results without having to re-run your program.

Gnuplot is a free plotting program that can plot datafiles and user-defined functions. It can't do everything you might possibly want, but it is very easy to use. This is a simple on-line guide to getting started with gnuplot.

Gnuplot expects data to be arranged in columns in an ordinary text file, for example:

# Gnu population in Antarctica since 1965 1965 103 1970 55 1975 34 1980 24 1985 10You can have as many columns as you like. Comments are indicated by "#".

To run gnuplot interactively, type:

gnuplotYou can also run gnuplot directly within UNIX, taking input from a file, e.g.

gnuplot < file.gnuwhere

You can get help by typing "?" or "help". The on-line help is very good.

You can abbreviate commands to save typing.

First, let's define a function:

pop(x) = 103*exp((1965-x)/10)Then we can plot this function, for x from 1960 to 1990, thus:

plot [1960:1990] pop(x)

To plot the datafile given above (assuming it is called population.dat),

plot 'population.dat'

And to plot both the function and the data,

plot [1960:1990] 'population.dat', pop(x)

By default, data files are plotted point by point. If you want lines joining the points,

plot 'population.dat' with linespIf you want lines only,

plot 'population.dat' w linesTo control which colour each set of lines and points comes out, see help plot. For example, to make the data come out with color 2 (dotted lines), and pop(x) with colour 1,

plot [1960:1990] 'population.dat' w lines 2 2, pop(x) w lines 1 1To plot column 4 of "flib.dat" against column 2 of the same file,

plot "flib.dat" u 2:4 w linesp(This gives column 2 on the x axis and 4 on the y axis.) You can also plot points with errorbars. This command plots column 4 versus column 2, with columns 5 and 6 defining the upper and lower error bars:

plot "flib.dat" u 2:4:5:6 w errorbars

The following sequence changes the terminal type to PostScript and
replots the most recent plot to a file called `file.ps`.

set term post set output "file.ps" replotDon't forget to set the terminal type back to X11 when you have finished plotting to the file:

set term X

In order to get graphs that are readable when included in papers, I recommend

set size 0.6,0.6before plotting to the file. This reduces the size of the graph while keeping the font size and point size constant.