Hi there! I'm trying to count the number of times coverage for various drugs (all of which have 0s for 'not covered' and 1 for 'covered) over time in each state (which its own categorical variable). I also have two date variables (mmddyyyy). Each date represents a new entry for coverage status for each drug in each state. There is no pattern to the entries for each state; instead, every time a drug's coverage changes, a new entry is made. There could be an entry on 10/01/2020 on which Montana's Medicaid covers say, alprazolam (i.e., alprazolman_var=1), but on 10/21/2020, alprazolam_var=0. This happens for each drug in the dataset and for each state. I'm just trying to count (1) the number of 'additions,' (i.e., drug_var=1 after drug_var was 0 in a previous entry for the state) and (2) subtractions (i.e., drug_var=0 after drug_var was 1 in a previous entry for the state) over time. I've tried using a lag function. I'd really like to be able to code for this rather than count manually!
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