Yes, that's my hope at the end. I want to be able to flag patients as switchers and non-switcher (stable) at a given date. For example, on July,1, 2013. At the beginning, I was just hoping to count how many times each patient switched and then sum up the total number of switches by pat_id before I use proc freq to get the distribution of the patients among drugs at a given date; Thank you very much again!
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