I have one more questions.  Lets assume the output for id is the following: 1 a-b 1 a-b-c 1 a-b-c-d  1 a-b-c-e 2 a-b 2-c-d  How can I create table the keeps only the highest combination for each id. I mean here we have a combintion of two drugs, three drugs, and four drugs.  I want to create a table that tell me the highest combination for patient 1 was 4 and for patient 2 is 2 and so on. Here is the output  1  4 2 2    ... View more

Super! Thank you ballardw and ksharp!  ... View more

KSHARP thank you! your code works perfect for the small dataset that has multiple medications for the same patient. Can one adjust the code if you have multiple ids? How can one modify the code if you have something like this with the first column be pt id?    1 a 01/01/2001 02/15/2001 1 b 01/02/2001 02/10/2001 1 c 04/05/2002 06/07/2002 1 d 04/15/2002 07/01/2002 1 e 04/01/2002 07/18/2002 1 f 04/05/2002 06/01/2002 2 a 01/01/2001 02/15/2001 2 b 01/02/2001 02/10/2001 2 c 04/05/2002 06/07/2002 2 d 04/15/2002 07/01/2002 2 e 04/01/2002 07/18/2002 2 f 04/05/2002 06/01/2002   ... View more

Ignoring patients ids, I am just trying to get aggregate numbers over a large data. I want to know the total number of prescriptions that overlap for 30 days or more.  If two medications overlap, then 2  if three medications overlap 3.  The output above shows the classes that overlaped. so for 2 a-b and so on  ... View more

Thank you!  ... View more

data one; informat start_date end_date mmddyy.; input id start_date drug $1. end_Date ; datalines; 1 01/01/2005 a 02/01/2005 1 02/02/2005 a 03/01/2005 1 03/08/2005 a 04/08/2005 1 06/01/2005 a 07/01/2005 2 01/01/2005 a 02/01/2005 2 02/02/2005 a 03/01/2005 2 03/08/2005 a 04/08/2005 2 06/01/2005 a 07/01/2005 3 01/01/2005 a 02/02/2005 ; run; also if the patient has one period with no other start date within 7 days (such as in patient 3), the code should assign that period as the start and end date for the output.  Thank you!  ... View more

if you have multiple ids, and you want to run the above code and generate the above output at the same time for multiple ids, how do you adjust your code for that? ... View more

Thank you Ksharp, always a life saver!  ... View more

Thank you for posting but you code does not produce the required output  ... View more