Date:         Thu, 19 May 2011 08:32:12 -0400
Reply-To:     "Bian, Haikuo" <HBian@FLQIO.SDPS.ORG>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Bian, Haikuo" <HBian@FLQIO.SDPS.ORG>
Subject:      Re: Drug Switching
Comments: To: Dave <david.brewer@UC.EDU>
In-Reply-To:  <201105191144.p4JAl4Oo000503@waikiki.cc.uga.edu>
Content-Type: text/plain; charset="us-ascii"

Dave;

Following code adopted 2XDUL, seems to work for you.

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;

data no_switch (drop=a b c flag) switched (drop=a b c flag);
retain a b flag;
do until (last.pid);
set in ;
by pid drug notsorted;
if first.pid then a=drug;
if last.pid then b=drug;
if a=b then flag=1;
else if a ne b then flag=0;
end;

do until (last.pid);
set in;
by pid drug notsorted;
    if flag=1 and first.pid then output no_switch;
    if first.drug and flag=0 then do;
                                 c+1;
                                 if c le 2 then output switched;
                                 end;

end;
c=0;
run;

proc print;
run;

HTH,
Haikuo

-----Original Message-----
From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of Dave
Sent: Thursday, May 19, 2011 7:45 AM
To: SAS-L@LISTSERV.UGA.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
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