gnuplot

* sci-visualization/gnuplot
Homepage: http://www.gnuplot.info/
Description: Command-line driven interactive plotting program

Gnuplot's web site has a large section with many examples. It also has a very detailed handbook. What it is lacking is a very simple tutorial to get people started.

From the start, you need to be aware that gnuplot can work in three modes: a fully interactive way, by loading a plot configuration file during an interactive session, or in a non-interactive way. We are going to explore each of these three ways.

To start an interactive session, simply type the command gnuplot, after which you will have a command prompt:

Now you are ready to operate in an interactive way, an easy and quick way to test some functions. The most important function is obviously plot. Try it:

After entering the command lot sin(x)/x, a window should have appeared with a picture on which the graph is plotted.

TODO: expand on interactive session, with the command replot.

But beyond making quick tests, it rapidly becomes tedious to work this way. The best is to create an input file, which you can edit and save (and even have under version control), and which you can load from within gnuplot.

Use your favorite text editor to create a file which you can name tutorial.gnuplot and save it:

The first line is obviously a comment, and the actual plotting command is on the second line.

Now you can use an interactive gnuplot session to load the file and execute its content:

To operate gnuplot so that an image is created straight away from your shell's command line prompt, you can set the output file in your .gnuplot file:

Then the following command will automatically create the image with the plot, non-interactively: