Date: Thu, 30 Aug 2001 12:18:55 -0400
Reply-To: "Dorfman, Paul" <Paul.Dorfman@BCBSFL.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: "Dorfman, Paul" <Paul.Dorfman@BCBSFL.COM>
Subject: Re: Automatically RETAINed ??
Content-Type: text/plain; charset=iso-8859-1
> So variables read with a SET are automatically retained. Right?
> Now consider the following (NT 8.0) log:
> 135 data a;
> 136 id=1;
> 137 x1=1;
> 138 x2=4;
> 139 run;
> 140 data b;
> 141 id=1;
> 142 x=3;
> 143 data c;
> 144 *retain;
> 145 set a b;
> 146 by id;
> 147 put _all_;
> 148 if (x1<=x<=x2);
> 149 run;
> id=1 x1=1 x2=4 x=. FIRST.id=1 LAST.id=0 _ERROR_=0 _N_=1
> id=1 x1=. x2=. x=3 FIRST.id=0 LAST.id=1 _ERROR_=0 _N_=2
> NOTE: There were 1 observations read from the dataset WORK.A.
> NOTE: There were 1 observations read from the dataset WORK.B.
> NOTE: The data set WORK.C has 0 observations and 4 variables.
> As you can see, 'data c' iterated twice. It was intended
> that the values of x1 and x2 from the first iteration
> be available in the second iteration. But they were
Yes, they were.
>I don't understand why. Please note that I get the same result if I
> the retain statement.
Because the values of x1 and x2 coming from B are missing values, and they
are missing NOT because they x1 and x2 were reset at the top of the step
(they were not), but because B does not have them at all. Logically, SAS
sets them to missing, and you are reading the interleaved file as if you
were reading a file created as
data x ;
id = 1 ; x1 = 1 ; x2 = 4 ; output ;
x1 = . ; x2 = . ; output ;
So, in the second iteration, the missing values simply overwrite x1=1 and
x2=4 in memory.
> No doubt I'm missing some important facts re the data step
> in interpreting the doc and/or composing the code.
> Where did I go wrong? :-)
Nothing, actually! You simply expected unexpected.
Paul M. Dorfman
Blue Cross Blue Shield of Florida, Inc., and its subsidiary and
affiliate companies are not responsible for errors or omissions in this e-mail message. Any personal comments made in this e-mail do not reflect the views of Blue Cross Blue Shield of Florida, Inc.