[Raro]

Python's NumPy library deliberately emulates much of the functionality of Matlab's core (similarly, fundamental plotting with matplotlib follow similar design cues). As a lapsed long-time Matlab user, I think they're just as fun to use.

There is also Octave, an open-source Matlab alternative, but when I last used it (admittedly quite a while ago) it had limited support for toolboxes (e.g. signal processing). I imagine it has only improved since.

[galangalalgol]

For elegant matrix syntax I like julia or fortran better, if I need a lack of a license or more speed. Octave is good too, but it is much slower than Matlab. Numpy is in a weird spot. Its still slower than Matlab, but its everywhere, but all the versions and environments are different so you need containers to be portable.