Date:         Fri, 16 May 1997 09:20:03 -0400
Reply-To:     Chris Roper <QLXCAR@AOL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Chris Roper <QLXCAR@AOL.COM>
Subject:      Re: PROC SUMMARY: CLASS with NWAY vs. BY
Comments: To: edheaton@fenix2.dol-esa.gov

Edward,
 
The CLASS statement will put all crossings of the variables listed into
memory, which can be a problem if you are dealing with very large datasets or
you have very tight memory constraints.  The BY statement expects that the
input dataset will be either sorted or indexed by the variables listed on the
BY statement.  Both will give you the same result, and on datasets of small
to moderate size it usually is just a matter of style as too which one you
use.  The printed output will be formatted a little differently with CLASS
creating a more compact format.  Personally, I use the CLASS statement unless
memory or efficiency becomes an issue, simply to save keystrokes, and because
I like the format of its printed output more.
 
 
Hope this helps,
 
Chris.
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