Carry observations foreward

[CharlotteH]

I am trying to carry observations foreward in observations where "number" is three or below. I want to create a new column where observations have been carried foreward and summed, so values in "new_number" are all above three.   

HAVE

Age      Number 

20        10

21         2

22         5

23         1

24         1

25         5

WANT

Age      Number      New_number

20        10               10

21        2                  .

22        5                  7

23        1                  .

24        1                  .

25        5                  7

[Astounding · Accepted solution]

One way:

data want;

set have;

running_total + number;

if running_total > 3 then do;

   new_number = running_total;

   running_total = 0;

end;

drop running_total;

run;