How can I create a variable that enumerates after the criteria is met?

[tampham92]

Hello,

This is a Have data and I want to generate Flag variable as seen in Wanted?

Have:

Date	Account ID	Flag
4/30/2022	1	0
5/31/2022	1	0
6/30/2022	1	0
7/31/2022	1	1
8/31/2022	1	0
9/30/2022	1	0

Want:

Date	Account ID	Flag
4/30/2022	1	0
5/31/2022	1	0
6/30/2022	1	0
7/31/2022	1	1
8/31/2022	1	2
9/30/2022	1	3

[Tom · Accepted solution]

Just use a SUM statement and the fact that SAS evaluates Boolean expressions to 1 for TRUE and 0 for FALSE.

data want;
  set have;
  by account date ;
  if first.account then new_flag=0;
  new_flag + (flag or new_flag);
run;

Result:

OBS    account          Date    Flag    new_flag

 1        1       2022-04-30      0         0
 2        1       2022-05-31      0         0
 3        1       2022-06-30      0         0
 4        1       2022-07-31      1         1
 5        1       2022-08-31      0         2
 6        1       2022-09-30      0         3

Note: You need to create a NEW variable for the RETAIN to work. If you try use a variable that is already on the input dataset then the retained value is lost when the next observation is read in.