Gnuplot is a portable command-line driven interactive data and function
plotting utility that supports lots of output formats, including drivers
for many printers, (La)TeX, (x)fig, Postscript, and so on. The X11-output
is packaged in gnuplot-x11.
Data files and self-defined functions can be manipulated by the internal
C-like language. Can perform smoothing, spline-fitting, or nonlinear fits,
and can work with complex numbers.
This package contains the additional documentation.