I was wondering what courses you can take in a pure math masters to preserve the opportunity to go into data science, economics, policy research or other applied work while preserving the opportunity to do pure math PhD later (keeping in mind that I can't take on a ton of extra coursework and would prefer to take classes that have some overlap on the math side, e.g. PDEs?). Are there standard computer science, statistics and/or applied math classes that give enough of a background to find data science work? I'll also take suggestions of any sort of course progression online, e.g. on Coursera, that could be helpful to do in parallel with my degree and are geared towards people with theoretical backgrounds but I worry that online courses won't be enough for employers.