Hello, I'm working with a wide dataset. Each row represents a person and includes treatment records as well as corresponding dates in which treatments are performed. My data essentially looks like this: ID treatment1 treatment2 treatment3 treatment4 treatment5 date1 date2 date3 date4 date5 John A B B B A Jan1 Jan15 Jan16 Jan17 Feb1 David A A B B A Jan1 March15 Jan5 Jan5 Feb15 What I need to do is for each person is to select the latest date in which he received treatment A (date5 for John and date2 for David in this case). I thought a simple array with a do-loop would do the trick but I realized that the dates1-5 are not necessarily recorded in chronological order. Any help would be greatly appreciated! Thanks!
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