Hi everyone, I have a dataset with a similar structure as the one shown below: data have; input PAT_ID RX_DT : ddmmyy10. RX_Name $; format RX_DT ddmmyy10.; datalines;; 201 18/07/2013 DrugA 201 27/12/2013 DrugA 201 13/06/2013 DrugC 201 19/08/2013 DrugC 201 01/05/2014 DrugC 201 14/10/2013 DrugC 201 20/02/2014 DrugC 201 27/03/2014 DrugA 201 16/09/2013 DrugB 201 18/12/2013 DrugC 202 16/04/2014 DrugC 202 16/01/2014 DrugC 202 02/10/2013 DrugC 202 15/07/2013 DrugC 202 13/05/2013 DrugC 202 11/03/2014 DrugB 202 11/11/2013 DrugB 202 23/09/2013 DrugA 202 05/08/2013 DrugA 202 24/06/2013 DrugA ; I would like to count the number of switches per patient from DrugA -> DrugB or from DrugB -> DrugA. For example, both patients have one swhitch. Thank you very much for your help in advance!
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