...for a mathematical computing course I'd like to offer:
matplotlib in Python3
R as one of the languages
This has been implemented. You can use matplotlib in python3 repl. And Heres the link to R repl (https://repl.it/languages/rlang)
We don't yet support R, but you can use matplotlib in python right now. Check out this blog post https://repl.it/site/blog/file-updates for an example.
sure thing, we'll add these two languages to our list :)