Well this may not be the fastest way but it will solve ur problem. Create a new variable in have Dataset. data have; n = _n_;  /* If obs number is present then rename it to n else create a new variable */      input id V1 V2; datalines; 1     2     2.1 1     0     2.9 1     2     3.1 2     4     1.7 2     0     4.5 2     0     0.5 2     5     2.8 ; data want2(keep = n); set have; n = _n_ ; if v1 = 0 then do;         output ;         n = n - 1 ;         output;      end; run; proc sort data = want2 nodupkey; by n; run; data want3; merge have(in= x) want2(in= y); by n; if x and y; drop n; run; ... View more