Please provide actual example data and expected results.  Are those supposed to be character strings?  So you should be able to use BY group processing and LAG(). data have; input existing $ @@; cards; A A A A A B B B B B B B C C C D D ; data want; set have; by existing notsorted; lag_existing=lag(existing); length new_variable $10 ; if first.existing then new_variable=catx('+',new_variable,lag_existing); retain new_variable ; drop lag_existing; run; If those are supposed to be numbers in looks like a running SUM. data have; input existing @@; cards; 2 2 2 2 2 1 1 1 1 1 1 1 3 3 3 5 5 ; data want; set have; by existing notsorted; lag_existing=lag(existing); length new_variable 8 ; if first.existing then new_variable=sum(new_variable,lag_existing); retain new_variable ; drop lag_existing; run;       ... View more

Use a DOW loop: data want; do until (last.b); set have; by b; c = max(c,a); end; do until (last.b); set have; by b; output; end; run; ... View more

If it's easier for you, then there is an option like this:   a                     b 1                     5 2                     5 3                     5 4                     5 5                     5 1                     4 2                     4 3                     4 4                     4   i have a i need b thank you!!! ... View more

Like this? ( sorry, but it's not clear to me what you want exactly )      Previous program had method=step.      Now I changed method=step into method=join. data work.class; set sashelp.class; datum = _N_; if mod(_N_,3) NE 0 then do; weight=.; height=.; end; run; PROC EXPAND data=work.class out=work.class_out method=join EXTRAPOLATE from=day to=day; id datum; convert weight = weight_out ; convert height = height_out ; run; /* end of program */ Koen ... View more