Hi,

You are getting extra flag because the input collection_date was string character and the sort order of the string gives different results when you compare > in your IF. Changing the incoming data to a real SAS date (by changing the informat to date11.) then lets your IF > statement work just fine.

data x; retain visit; input patient $10. visit $3. collection_date date11.; format collection_date date9.; cards; 0004 00001B0116-JAN-2002 0004 00001B0313-FEB-2002 0004 00001B0509-FEB-2002 0004 00001B0802-JUL-2002 0004 00001B1027-AUG-2002 0004 00001B9917-SEP-2003 0004 00001C0113-NOV-2002 0004 00001C0706-MAY-2003 ; run;

data xx; set x; if visit>lag(visit) and collection_date<lag(collection_date) then flg='NR'; run;

Hope this is helpful.

Mark Terjeson Senior Programmer Analyst, IM&R Russell Investment Group

Russell Global Leaders in Multi-Manager Investing

-----Original Message----- From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of Sridhar, Kumar Sent: Thursday, February 16, 2006 12:11 PM To: SAS-L@LISTSERV.UGA.EDU Subject: Help with lag

Hi All:

Here's a question that a colleague asked me and since I was stumped, I decided to ask you folks.

data x;

retain visit;

input patient $10. visit $3. collection_date $11.;

cards;

0004 00001B0116-JAN-2002

0004 00001B0313-FEB-2002

0004 00001B0509-FEB-2002

0004 00001B0802-JUL-2002

0004 00001B1027-AUG-2002

0004 00001B9917-SEP-2003

0004 00001C0113-NOV-2002

0004 00001C0706-MAY-2003

;

run;

If you observe, the third observation has a date of 09-FEB-2002 which is earlier than the previous visit but the visit number is greater. I want to put a flag on those observations (in this case the 3rd one) where the date is earlier than the previous visit.

I tried the following but it puts a flag on all observations so any input from you to correct the code would be really appreciated.

data x;

set x;

if visit>lag(visit) and collection_date<lag(collection_date) then flg='NR';

run;

proc print;

run;

Kumar