Date:         Fri, 26 Sep 2003 07:39:51 -0700
Reply-To:     Lex Jansen <spam@LEXJANSEN.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Lex Jansen <spam@LEXJANSEN.COM>
Organization: http://groups.google.com/
Subject:      Re: Data Step Question
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You could also do a search for "data step" on my Google powered SUGI
page at http://www.lexjansen.com/sugi
It will also give you the opportunity to search the NESUG papers.

HTH,

Lex Jansen

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ben.powell@CLA.CO.UK (Ben Powell) wrote in message news:<200309260858.h8Q8wKv03922@listserv.cc.uga.edu>...
> Thanks Matt and others. I expect I introduced an error in naming variables
> hence why the datastep would not work and why I broke it up - making it
> inefficient, though not so much of an issue on datasets of less than 100k
> rows - before finally getting round to putting it back together here!
>
> Thanks also for the tip on the Datastep Manual -- can you suggest a good
> one, preferably that would be available from the UK as otherwise I'd be
> paying express US postage from fatbrain.com or somesuch, which frankly
> spoils the party,
>
> Best Regards.
>
> Date:    Thu, 25 Sep 2003 14:01:50 -0700
> From:    m n <iced_phoenix@YAHOO.COM>
> Subject: Re: Data Step Question
>
> ben.powell@CLA.CO.UK (Ben Powell) wrote in message
> news:<200309251339.h8PDd3v01281@listserv.cc.uga.edu>...
> > I'm not clear on what can be done in any single datastep and would
> > appreciate any pointers.
> >
> > Say for example I want to copy a dataset to my work lib, rename a
> > variable and keep that and one other variable. Because in the past I
> > have found that sometimes a step won't action unless there is a run
> > command after it I would break this job into 3 seperate data steps,
> > which is quite repetative. Is there a rule of thumb for when a new
> > datastep is needed and how many steps can be included in a datastep?
> >
> > e.g.
> >
> > data a;
> > set lib.a;run;
> > data a (rename=(var1=var2));
> > set a;run;
> > data a;
> > set a;
> > keep var2 var3;
> > run;
>
> Hi Ben,
>
> It seems that there's a misunderstanding of the data step at work here.
> Reading any good SAS Data Step programming manual will help; in the mean
> time, perhaps it will help to note a couple properties of the data step:
>
> * Each data step is a separate program; it is compiled and executed
> separately from every other step in your SAS job.  Thus, once you start
> thinking of the data step as a separate program in its own right, you can
> start to exploit its tremendous power.
>
> * Each data step is an implicit loop.  A SAS Data Step manual will explain
> A LOT about this fundamental concept.
>
> In the meantime, other posters solved your problem using data set options.
> To give you some further insight, the same thing could be accomplished with:
>
> data a;
>   set lib.a (rename (var1=var2));
>   keep var2 var3;
> run;
>
> Picture the above data step as a loop, each iteration reading in one
> observation from lib.a (via the set statement) and simultaneously renaming
> var1 to var2, then outputting only var2 and var3.  You can do a tremendous
> amount of other processing in this implicit loop; each iteration of the
> loop will carry out the processing on just the current observation.
>
> I hope that helps,
> Matt