Date:         Wed, 14 May 2008 12:05:05 -0700
Reply-To:     jn mao <jn_mao@YAHOO.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         jn mao <jn_mao@YAHOO.COM>
Subject:      How to generate a delta variable in longitudinal data
In-Reply-To:  <6a180f91-61e7-40c4-b9bb-ffb14b07d7ec@24g2000hsh.googlegroups.com>
Content-Type: text/plain; charset=iso-8859-1

Hello SAS-Ls,

  I have a longitudinal data file. There are 10 time points, I need to generate a new variable that is the difference of the value of the old variable between each time point and the baseline time point. How do I generate it?

  The original data format:
  Id  Time   Var1
  1    0         10
  1    10        12
  1    20        11
  1    30        17

  The data I want:
  Id  Time  Var1   Delta1
  1    0        10     0 (10-10)
  1    10      12     2  (12-10)
  1    20       11    1 (11-10)
  1    30      17     7 (17-10)

  Could someone help me on SAS code for generating Delta1? Thanks much!

  Jane