I have a bachelors in economics and am playing with the idea of returning to school for applied math or statistics. What would I have to do to get into graduate school? Would I have to return to school as an undergrad and get a second bachelors? Or is it possible to just take a few upper level math classes for recommendations and then take the subject GRE? I only took up to differential equations and would have a lot to learn but I always regretted not switching majors. Thanks!