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Re: st: Setting a reference value by rows for calculating differences


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Setting a reference value by rows for calculating differences
Date   Fri, 17 Jun 2011 08:57:13 +0200

On Fri, Jun 17, 2011 at 8:45 AM, CHERYL BARNABE <ccbarnab@ucalgary.ca> wrote:
> Hi there, trying to calculate the elapsed time from the baseline (or 1st visit) for each subject to subsequent follow-up visits, not the prior visit, but can't figure out the command to keep the first entry per subject as the reference
<snip>
> by study_id: generate visitmonth=(visitdate-visitdate[_n==1])

that should be:
by study_id: generate visitmonth=(visitdate-visitdate[1])

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany


http://www.maartenbuis.nl
--------------------------
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