Hello experts,   I would greatly appreciate your help with this issue I am having. I need to keep the first occurrence of code change that happens in my dataset.  I have created a sample of the data I am working with below. For ID 001 we want the SEQ 3 for it. This is the first time they were changed to their current code which you can see they are still on with their recent "review" from observation 1 and date of 05/04/2014. For 002 we would need to keep SEQ 2 for them.   I have tried to sort and duplicate out the observation not in the first group of 'ST' but the issue I have is if in their history they were on that code before the older dates get mixed in and those are two separate occurrences. I have no data point to separate the occurrence other than a different status happening in between, such as we see with 'GP' on observation 4. I also tried to count the number of ST's in the group and stop when it reaches GP but I had no such look due to needing a by statement and the sort has the issues mentioned above.    In short, I need a piece of code that can identify the first occurrence of their most recent Code, here it is ST but I also have SP and DD. For ID 001 observation line 3 is the one needed to keep and for 002 observation line 7 is the one to keep.   Thanks for any help I can receive.    P.s. Do note the format of the date is ddmmyy.     data want; input ID SEQ Code $ date :ddmmyy10.; format date ddmmyy10.; datalines; 001 1 ST 05/04/2014 001 2 ST 05/01/2014 001 3 ST 04/01/2014 001 4 GP 02/05/2014 001 5 ST 02/01/2014 002 1 ST 05/01/2014 002 2 ST 03/02/2014 002 3 GP 02/01/2014 002 4 GP 02/01/2014 ; run; ... View more