This short article explain two ways to use GNU Octave, the world-famous free and open-source software, the most serious alternative to MATLAB (SciLab is also a good FOSS alternative, if you are interested).
Both solutions are free to use, and should work on any modern browser (desktop for sure, mobile not so much).
A pretty good web-application, kinda ugly styled, but work really well. The script or the figures can be saved on your desktop if neeeded.
They offer quite a lot of free to use web-applications, and Octave is one of them: Octave on NClab.com. It also work pretty well!
Avis
The links to their webapp could change, so if it is broken, you can find it on their web-applications page.
I tried to find an easy-to-install Octave interpreter in Javascript (to embed on a webpage here), but found none. I will keep looking once in a while, and I ever find one, it will be included here.
In the mean time, did you know that there is already two online interpreters on my website, one for Python, one for OCaml and one for GNU Plot ?