GNU Octave is a cross-platform Open Source alternative for the famous Matlab. Octave uses the same commands as Matlab and it’s an excellent free alternative. The new version 3.0 was released the past December 21st. The most significant changes have been the improvements of graphics (like controling the width of lines, RGB line colors are supported, the possibility of making a subplot and then use the print function to generate file with the plot, …), path handling and built-in variables. You can check out all the notable changes in the Octave official site.