Gnuplot is the most widely used open-source program to plot and visualize data. It's available for nearly every major platform. Gnuplot handles both curves (2 dimensions) and surfaces (3dimensions). Graphs may be labeled with arbitrary labels and arrows, axis labels, a title, date and time, and a key. Gnuplot supports many different types of terminals, interactive screen terminals (with mouse and hotkey functionality), direct output to pen plotters or modern printers (including many color devices, and pseudo-devices like LaTeX), output to many file formats (eps, fig, jpeg, LaTeX, metafont, pbm, pdf, png, postscript, svg, ...) and is easily extensible to include new devices. It can be operated in one of two modes: when you need to adjust and prettify a graph to "get it just right," you can operate it in interactive mode by issuing commands at the gnuplot prompt. Alternately, gnuplot can read commands from a file and produce graphs in batch mode. Batch-mode capability is especially useful if you are running a series of experiments and need to view graphs of the results after each run, for example; or when you need to return to a graph to modify some aspect long after the graph was originally generated. Beacuse of Gnuplot is a command-line driven interactive function plotting utility, a graphical user interface (GUI or front-end) could be useful;

Software that use Gnuplot are Maxima (see functions, images and so on) and Octave. Notice: the "GNU" in Gnuplot is not related to the Free Software Foundation, the naming is just a coincidence. Terms of license are Freely Distributable; this software may be distributed freely, but restrictions have been placed on your right to modify it and so on. Please see the author(s)/license(s) file for details.