topic Re: Delete consecutive observations if same in SAS Procedures

Delete consecutive observations if same

Statsconsultancy — Fri, 14 Aug 2009 15:53:55 GMT

My data set has the following form:

subject treatment dateprescribed
1 A 08/08/1997
1 A 09/12/1998
1 A 12/01/1999
1 B 07/09/2000
1 B 05/09/2001
1 A 05/06/2002
1 A 06/10/2002
1 A 09/11/2003
2 A 08/03/1996
2 A 09/12/1998
2 B 12/01/1999
2 B 07/09/2000
2 B 05/09/2001
2 A 05/06/2002
2 A 06/10/2002
2 B 09/11/2003

I want to delete the row if the treatment in that row is the same as the
previous treatment; Thus I want to obtain the following:
subject treatment dateprescribed
1 A 08/08/1997
1 B 07/09/2000
1 A 05/06/2002
2 A 08/03/1996
2 B 12/01/1999
2 A 05/06/2002
2 B 09/11/2003

Thus patient 1 received the treaments in the order ABA, while patient 2 received the treatments in the order ABAB . Can someone help me on how to do that in SAS.

Best wishes

Re: Delete consecutive observations if same

Flip — Fri, 14 Aug 2009 18:06:37 GMT

Sort by subject treatment dateprescribed.

data xxx;
by subject treatment dateprescribed;
if first.treatmant;
run;

Re: Delete consecutive observations if same

SUN59338 — Fri, 14 Aug 2009 18:18:48 GMT

May also;

data result;
set old;
if subject = lag(subject) and treatment = lag(treatment) then delete;
run;

Re: Delete consecutive observations if same

ballardw — Tue, 18 Aug 2009 22:51:03 GMT

Or this may work:

Proc Sort data=old out=new noduprecs; by x y z;run;

Re: Delete consecutive observations if same

data_null__ — Thu, 20 Aug 2009 13:19:58 GMT

> Sort by subject treatment dateprescribed.
>
> data xxx;
> by subject treatment dateprescribed;
> if first.treatmant;
> run;

This wont work because the data need to be ordered by date, not treatment. But, the FIRSTing needs to be done by TREATMENT. The NOTSORTED by statement option is the key.

[pre]
data rx;
input (subject treatment dateprescribed)(2*:$1. :mmddyy.);
format date: mmddyy10.;
cards;
1 A 06/10/2002 I mixed up the lines a bit
1 A 09/11/2003
1 A 08/08/1997
1 B 07/09/2000
1 B 05/09/2001
1 A 05/06/2002
1 A 09/12/1998
1 A 12/01/1999
2 A 08/03/1996
2 A 09/12/1998
2 B 12/01/1999
2 B 07/09/2000
2 B 05/09/2001
2 A 05/06/2002
2 A 06/10/2002
2 B 09/11/2003
;;;;
run;
proc sort;
by s: d:;
run;
proc print;
by s: t: notsorted;
id s: t:;
var d:;
run;

data firstInSequence;
set;
by s: t: notsorted;
if first.treatment;
run;
proc print;
by s:;
id s:;
run;
[/pre]