Wikipedia
Plotutils
GNU plotutils is a set of free software command-line tools and software libraries for generating 2D plot graphics based on data sets. It is used in projects such as PSPP and UMLgraph, and in many areas of academic research, and is included in many Linux distributions such as Debian and cygwin. Windows and Mac OS X versions are also available. The library provides bindings for the C and C++ languages. Its stand alone command-line tools can generate graphs and perform numerical calculation of spline curves and systems of ordinary differential equations. Plotutils is a GNU package and is distributed under a free software licence, the GPL.