Selecting time-frame for observations

[cyoung]

Hello again,

I was wondering if anyone can help point me in the direction of what code I should try to make what I'm hoping for work. 

Basically, I have observation in Person-Months for a span of 5 years (i.e. ID1-1... ID1-60, ID2-1... ID2-60, etc.).  I have a variable that indicates an event of interest during the month, and I was hoping to create a new dataset that has data only from 2 years after the first event.  I've tried using a IF/THEN with a KEEP statement, but am having trouble identifying the two years post event.

For reference, my dataset has 3 variables: ID, MonthYear, and Event (binary)

Does anyone have an idea?

[art297 · Accepted solution]

If your data are already in id, monthyear order (otherwise if you sort it to be in that order), then I think that the following will do what you want:

data want;
  set have;
  by id;
  if first.id then counter=0;
  if counter eq 0 and event eq 1 then do;
    counter=1;
    output;
  end;
  else if 1<=counter<=24 then do;
    counter+1;
    output;
  end;
run;

Art, CEO, AnalystFinder.com

[cyoung]

That worked perfectly!  Thank you so much!!