Cheers, I have a dataframe of IDs that has a specific order. I need a rolling count of IDs for each ID. Below my example has 2 IDs with 2 other data fields in order. The Count field is what I need to add to the dataframe: ID Value_1 Value_2 Count 1234 x a 1 1234 x b 2 1234 y c 3 2222 s a 1 2222 t b 2 Thanks, Bob