Hi All, I am new to sas and I was trying to achieve such thing:   here is the dataset: PERMNO EVTDATE first_event inter_event 10001 8/1/11 1 0 10001 4/2/12 0 1 10002 7/6/98 1 0 10002 10/27/98 0 1 10011 11/13/95 1 0 10011 5/28/96 0 1 10011 5/29/96 0 1 10016 12/9/99 1 0 10016 5/3/00 0 1 10020 4/6/87 1 0 10020 10/21/87 0 1 10020 12/11/87 0 1 10020 4/17/90 1 0 10020 4/24/90 0 1 10028 8/17/99 1 0 10028 3/3/00 0 1 10028 7/14/06 1 0 10028 5/10/07 0 1 I would like to create another column call program and the column will state as: PERMNO EVTDATE first_event inter_event define a program, and numbers of event in the group 10001 8/1/11 1 0 2 10001 4/2/12 0 1 2 10002 7/6/98 1 0 2 10002 10/27/98 0 1 2 10011 11/13/95 1 0 3 10011 5/28/96 0 1 3 10011 5/29/96 0 1 3 10016 12/9/99 1 0 2 10016 5/3/00 0 1 2 10020 4/6/87 1 0 3 10020 10/21/87 0 1 3 10020 12/11/87 0 1 3 10020 4/17/90 1 0 2 10020 4/24/90 0 1 2 10028 8/17/99 1 0 2 10028 3/3/00 0 1 2 10028 7/14/06 1 0 2 10028 5/10/07 0 1 2   let say for permno 10001, there are two obs and they form a program and the program has two event in a row, so it will be definded as 2 for each of the two obs.   Thank you so much for your help! Appreciated, Zhongda   ... View more