I never used MATLAB before, so I don’t know how powerful it is. In order to plot graph and perform calculation, these are some applications may be interesting,
- R – It is also called R programming language, used for statistics
- Octave – Alternative to MATLAB
- FreeMat – Alternative to MATLAB
- Sage – A large size application, considered as an alternative to Mathematica and MATLAB
Another one I like is Python with SciPy and matplotlib. They are pretty awesome.