Date: Mon, 14 Jul 2003 14:07:44 -0700
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: "David L. Cassell" <cassell.david@EPAMAIL.EPA.GOV>
Subject: Re: Proc Genmod
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John Conway <jpconway2@COMCAST.NET> wrote [once again]:
> This is a multi-part message in MIME format.
Please stop doing that. This venue is a mailing list, a UseNet group,
and a digest service. Sending MIME (and sending more than one post
of exactly the same message) actually causes problems for large numbers
of participants. Thanks in advance.
> Does Proc Genmod have the facility for either forward or backward
No. PROC GENMOD is not a simple linear model, so the traditional
selection methods and rules of thumb would not be appropriate. If they
Furthermore, I salute SAS for *not* having any forward/backward/
in PROC GENMOD. They are too badly abused in PROC REG as things are.
I have written _ad_nauseam_ on the subject in this venue, but all too
these tools are misused and abused in hideous ways, causing the user to
up with a nice-looking formula.. which predicts nothing and is chockful
misleading numbers. Add in an arbitrary number of potential link
and response probability distributions, and a mathematical search for an
'ideal' equation becomes an exercise in improperly attributing meaning
the most serious outliers and most egregious leverage points. Please,
*please* do not go this route.
If you are searching for a way of modeling with many collinear
then perhaps you should look at PROC PLS instead. That might be more
than listening to me gripe endlessly. :-)
David Cassell, CSC
Senior computing specialist