Date:         Tue, 6 Dec 2005 15:55:01 +0000
Reply-To:     toby dunn <tobydunn@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         toby dunn <tobydunn@HOTMAIL.COM>
Subject:      Re: Eliminating rows, based on date values
Comments: To: jim1stat@YAHOO.CO.UK
In-Reply-To:  <200512061551.jB6EsDVx020379@mailgw.cc.uga.edu>
Content-Type: text/plain; format=flowed

Jim,

I thought it was 30 days but it seems I miss read it should be 90 days.

As for the code I must be having a bad day your right there too my man:

LastDate = Lag(SASDate) ;

If not first.Var_a then do ;
   if ( ( SASDate - LastDate ) < 90 ) then delete ;
end ;

Should fix the problem.


Now with those screw ups out of the way I am going to go over here and sit
quitely on my corner...before I make anymore screw ups today.




Toby Dunn





From: Jim Groeneveld <jim1stat@YAHOO.CO.UK>
To: SAS-L@LISTSERV.UGA.EDU, Toby Dunn <tobydunn@HOTMAIL.COM>
Subject: Re: Eliminating rows, based on date values
Date: Tue, 6 Dec 2005 10:51:24 -0500
Hi Toby,

Good idea, but shouldn't 30 be 90 as Tomas requested?
And very important: do not use the LAG function conditionally!
Calculate the LAG initially ouside the IF block!

Regards - Jim.
--
Y. (Jim) Groeneveld, MSc., Biostatistician, Vitatron b.v., NL
Jim.Groeneveld_AT_Vitatron.com (replace _AT_ by AT sign)
http://www.vitatron.com, http://home.hccnet.nl/jim.groeneveld

My computer regards me as its master, but I seem to be its slave.

[common disclaimer]

On Tue, 6 Dec 2005 15:44:18 +0000, toby dunn <tobydunn@HOTMAIL.COM> wrote:

 >Tomas,
 >
 >Try something like:
 >
 >If not first.Var_a then do ;
 >  if ( SASDate - Lag(SASDate) ) < 30 then delete ;
 >end ;
 >
 >Essentually SAS date values are scalers, where they measure the number of
 >days from january 1, 1960.  So provided you have the dates in SAS Date
Value
 >Form Which it looks like you do, then  all you need to do is get the last
 >data value and then substract, if that is less than 30 then delete.
 >The do loop is designed so that you dont do this comparison on the first
 >obeservation of a new Var_a Group.
 >
 >Toby Dunn
 >
 >
 >
 >
 >
 >From: Tomas <tomas.corveleyn@GMAIL.COM>
 >Reply-To: Tomas <tomas.corveleyn@GMAIL.COM>
 >To: SAS-L@LISTSERV.UGA.EDU
 >Subject: Eliminating rows, based on date values
 >Date: Tue, 6 Dec 2005 07:29:28 -0800
 >
 >
 >Dear,
 >
 >I'm trying desperately to eliminate rows from the following type of
 >file:
 >
 >obs       var_a Date    Sasvalue(date)
 >   1             1       2/apr/02            15432
 >   2             1       12/jun/03           15868
 >   3             1       13/jun/03           15869
 >   4             1       14/jun/03           15870
 >   5             1       15/jun/03           15871
 >   6             1       16/jun/03           15872
 >   7             2       26/mar/02           15425
 >   8             2       11/sep/03           15959
 >   9             3       1/jan/03            15706
 >
 >With var_a being the id for a person. Based on the variable "Date" or
 >the Sasvalue of that variable, I want to eliminate observations 3 to 6.
 >I do not want to end up with only one observation per person, I want to
 >keep the observations between which there are at least 90 days! So, my
 >end-file has to be the following:
 >
 >obs       var_a Date    Sasvalue(date)
 >   1             1       2/apr/02            15432
 >   2             1       12/jun/03           15868
 >   7             2       26/mar/02           15425
 >   8             2       11/sep/03           15959
 >   9             3       1/jan/03            15706
 >
 >I've tried "retain" statements working on the Sasvalue of the
 >datevariable, but I haven't been able to compute the correct formula
 >which eliminates only observations 3 to 6. Or I eliminate to much, or I
 >eliminate to little. Can someone help me with this problem?
 >
 >Many thanks,
 >
 >Tomas Corveleyn.