Loop with a lag function

eemrun — Tue, 21 Mar 2023 00:48:26 GMT

I need to calculate rows with a lag variable but struggling to do that. Essentially it should follow this function

For first row, D = A+B

For subsequent rows, D = lag(D)+A

Any guidance?

Re: Loop with a lag function

Tom — Tue, 21 Mar 2023 01:02:48 GMT

No LAG() needed. Just make sure D is a NEW variable and RETAIN its value.

data want ;
  set have;
  retain d;
  if _n_=1 then d=a+b;
  else d=d+a ;
run;

eemrun — Tue, 21 Mar 2023 01:50:32 GMT

Oh brilliant! So simple. Thanks so much!