Gnuplot is a portable multi-platform command-line driven graphing utility. It
was originally created to allow scientists and students to visualize
mathematical functions and data interactively, but has grown to support many
non-interactive uses such as web scripting. It is also used as a plotting engine
by third-party applications like Octave. Gnuplot has been supported and under
active development since 1986.

Gnuplot supports many types of plots in either 2D or 3D. It can draw using
lines, points, boxes, contours, vector fields, surfaces, and various associated
text. It also supports various specialized plot types. Gnuplot supports many
different types of output: interactive screen terminals (with mouse and hotkey
input), direct output to pen plotters or modern printers, and output to many
file formats (eps, emf, fig, jpeg, LaTeX, pdf, png, postscript, ...). Gnuplot is
easily extensible to include new output modes. Recent additions include
interactive terminals based on wxWidgets (usable on multiple platforms), and Qt.
Mouseable plots embedded in web pages can be generated using the svg or HTML5
canvas terminal drivers.

WWW: http://www.gnuplot.info/