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Date:         Mon, 25 Feb 2008 02:56:40 -0800
Reply-To:     Sylar <rifazrazeek@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Sylar <rifazrazeek@GMAIL.COM>
Subject:      Re: Calculating Days Since Last Visit
Comments: To:
Content-Type: text/plain; charset=ISO-8859-1

Hi David,

Yes, LAG function would be an easy way to do it.

See some code below.

Hope it helps. Rif

======================================= data dset1; input patient date date9.; format date date9.; datalines; 1 01JAN08 1 08JAN08 1 14JAN08 2 02JAN08 2 09JAN08 2 15JAN08 ; RUN;

proc sort data=dset1; by patient; run;

data dset2; set dset1; by patient; last_visit=lag(date); if first.patient then last_visit=.;

days_since_last_visit=date-last_visit; format last_visit date9.; run; ==============================================

On Feb 25, 9:06 am, harrypotter...@EARTHLINK.NET (David Friedman) wrote: > For a given patient visit I want to calculate the days since last visit. I > have several visit records per patient. I want to get output something > like this: > > Patient # Visit Date Days since last visit > 1 1/1/2000 . > 1/8/2000 7 > 2/1/2000 30 > > What is the best way to do this? Lag function?

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