Here's a solution. Note that you do not need the retain in the first data step and you will need to read the dates as SAS date values.

Nat Wooding

data x;

* retain visit;

input patient $10. visit $3. collection_date date11.; format col: mmddyy10.;

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 y; set x; lastvisit=lag(collection_date); format col: lastvisit mmddyy10.; if lastvisit gt collection_date then flag='*'; proc print; run;

"Sridhar, Kumar" <nsridhar@MEDAREX .COM> To Sent by: "SAS(r) SAS-L@LISTSERV.UGA.EDU Discussion" cc <SAS-L@LISTSERV.U GA.EDU> Subject Help with lag

02/16/2006 03:10 PM

Please respond to "Sridhar, Kumar" <nsridhar@MEDAREX .COM>

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

----------------------------------------- CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and/or privileged and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an additional express written confirmation to that effect. The information is intended solely for the individual or entity named above and access by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or use of the contents of this information is prohibited and may be unlawful. If you have received this electronic transmission in error, please reply immediately to the sender that you have received the message in error, and delete it. Thank you.