GNU Octave is a high-level language, primarily intended for numerical computations. It provides a convenient command line interface for solving linear and nonlinear problems numerically, and for performing other numerical experiments using a language that is mostly compatible with Matlab. It may also be used as a batch-oriented language.
xd3d is a simple scientific visualization tool designed to be easy to learn. It can plot 2d and 3d meshes, with shadowing, contour plots, vector fields, iso-contour (3d), as well as 3d surfaces z=f(x,y) defined by an algebraic expression or a cloud of points. It generates high quality vector PostScript files for scientific publications and still or animated bitmap images. It includes the graph plotter xgraphic.