Date:         Fri, 3 Dec 2010 15:05:34 -0500
Reply-To:     Joe Zhou <g75wez1@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Joe Zhou <g75wez1@GMAIL.COM>
Subject:      Replacing missing values by the previous non-missing value

Hello all,

I need your SAS expertise in terms of replace the missing
values by using their previous non-missing values within a group.

Have a data like:

data have;
  input q1 q2 q3 q4;
 cards;
1 1 1 10
. . 2 11
. 2 1 200
. . 2 201
2 1 1 100
. . 2 101
. 2 1 2000
. . 2 2001
;

Wanted data:
1 1 1 10
1 1 2 11
1 2 1 200
1 2 2 201
2 1 1 100
2 1 2 101
2 2 1 2000
2 2 2 2001

Thank you very much for your helps.


Joe