Date:         Thu, 19 May 2011 07:44:36 -0400
Reply-To:     Dave <david.brewer@UC.EDU>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Dave <david.brewer@UC.EDU>
Subject:      Drug Switching

Hi SAS-Lers

I need to find out which patient switched drugs and also if they switched
determine the first time they switched.

data in;
 input pid drug date:mmddyy10.;
 format date mmddyy10.;
 cards;
1 1234 1/1/2010
1 1234 2/1/2010
1 1234 3/1/2010
2 34   3/5/2010
2 34   4/1/2010
2 45   5/2/2010
2 56   6/3/2010
3 55   4/1/2010
3 56   5/1/2010
3 57   6/1/2010
3 57   7/1/2010
4 123  6/3/2010
5 55   7/1/2010
5 55   7/24/2010
;
run;

Since pid 1, 4, and 5 never switched they would be outputted to NO_SWITCH
data set.

PID 2 had an initial switch from date 3/5/2010 and 5/2/2010; i.e., changed
drugs from 34 to 45. I need to output those two records to data set
SWITCHED.

PID 3 would output drug 55 and 56 to data set SWITCHED.

Any suggestions?

Thanks for your help.
Dave