I'm writing code to flag data.  In this one dataset, we have medical kits supplied to different subjects. each subject comes in somewhere between 1 to 8 times, and each visit is labeled as V1-V8. i need to make sure that the id number on a medical kit given to a subject on his last visit, matches the same one he received on his prior visits.    ex: Kit#     Subject     Visit 22        01             V1 22        01            V2 44        02            V1 45        02            V2   in the example, subject one would be fine, because they were given the same medical kit. Subject 2 would flag, because they were given a different medical kit than in previous visits. ... View more