Date:         Tue, 9 Mar 1999 20:17:08 +0100
Reply-To:     Bas Pruijn <bas.pruijn@CMG.NL>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Bas Pruijn <bas.pruijn@CMG.NL>
Subject:      Re: carrying data forward
Comments: To: John Whittington <medisci@POWERNET.COM>
Content-Type: text/plain

I think I simplified a little to much. I have overlooked the subject part.
You're also right about the retain. Sorry for the reply without enough
thought.
 
> -----Original Message-----
> From: John Whittington [SMTP:medisci@POWERNET.COM]
> Sent: Tuesday, March 09, 1999 5:57 PM
> To:   SAS-L@AKH-WIEN.AC.AT
> Subject:      Re: carrying data forward
>
> At 17:19 09/03/99 +0100, Bas Pruijn wrote:
>
> >data outfil;
> >  set infil;
> >  retain var1 var2 var3;
> >run;
>
> Bas, unfortunately it's not as easy as that.  All RETAIN does is stops the
> variables being 'reset to missing' at the 'top' of each iteration of the
> DATA step.  The previous value will therefore only be RETAINed until such
> a
> time as a new value is assigned to the variable - in this case by the SET
> statement - at which point the variable will acquire the 'new' value, no
> matter what its value (even 'missing').
>
> Furthermore, even if RETAIN did what you prtesumably thought it did, your
> code would have potentially resulted in values being 'carried forward'
> from
> one subject to a totally different subject.  I don't think there is any
> simpler way of achieving what is needed than the code I posted recently.
>
> Kind Regards,
>
> John
>
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