calculate time span between the first and last date within 2 variables group

[michellel]

Hi,

I have a question related to calculate time span between the first and last date within 2 variables group. My data looks like below, sorted by student_id test_id date. I need count time span between the first and last date for each test_id of each student_id. Thanks much in advance for your help!

My data:

student_id	test_id	date
aaa	123	05/06/2012
aaa	123	06/07/2012
aaa	123	02/06/2013
aaa	345	12/17/2012
aaa	345	07/22/2013
aaa	345	11/11/2013
bbb	234	02/29/2012
bbb	234	05/30/2012
bbb	789	07/19/2013
bbb	789	07/31/2013
bbb	789	09/30/2013

What I want is:

student_id	test_id	time_span
aaa	123	276
aaa	345	329
bbb	234	91
bbb	789	73

[PGStats]

Please fix your data. 

[ballardw · Accepted solution]

Try this:

proc summary data=have nway;
   class student_id test_id;
   var date;
   output out=want(drop=_:) range(date)=time_span;
   format date best6.;
run;

[michellel]

Thanks ballardw! best4. works as well. I did not realize how to fix my data as PG pointed until you told me that DATE variable has a date format attached the result will look funny. Thanks!