[fithisux]

Octave has served many and many students and has been the go to alternative for undergraduates for years.

It is a great example of GNU's contribution to the advancement of human kind.

It is highly recommended for numerical mathematics and can be extended with GNU-Fortran or GNU-C. It comes bundled with many extensions.

It is mostly a DSL for numerics.

Scilab is another recommended similar package but comes with less extensions.