I’m trying to find which qualifying part was treated after the first visit for the 2nd and 3rd visit but have hundreds of entries. I have tried encoding the parts and using bysort to try and solve this but unsure how to keep it per person per visit…

For each person (id 301, 302, 303, etc), each visit (1 2 3), a list of problems (1-4) by body part (by system) were given. Out of these body parts, the qualifying part (q_part) was treated at the first visit. There can be more than 1 qualifying part per visit and qualifying parts can skip a visit.

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