Hi.   I'm using SAS 9.4 and have a programming question (I'm also quite new to SAS).   I want to "flag" all numbers from 4 to the first 0 in the diff_brunst variable by creating ones in the length variable, how do I do that?    This is the code I have been trying.    data c; set b; if diff_brunst = 4 then do length = 1 until (diff_brunst = 0); end; else length = 0; run; Output (form a huge dataset).  In the parentheses is what I want to achieve.   Diff_brunst  Length 0                  0 0                  0 0                  0 0                  0 0                  0 2                  0 3                  0 4                 1 (1) 5                  0(1) 6                  0(1) -5                 0(1) 0                  0(1) 0                  0 0                  0 0                  0 ... View more