Re: [R] A regression problem using dummy variables

From: Bert Gunter <>
Date: Thu, 03 Jul 2008 07:21:04 -0700

Contrasts for categorical variables are a technical issue in linear models. They are best understood (imo) as the choice of bases for the vector space of the model matrix. So how good is your linear algebra? A terse but I think very clear treatment of these issues can be found in the relevant chapter of V&R's MASS book.

FWIW, I have found that even statisticians get confused by these issues (certainly I have!).

-----Original Message-----
From: [] On Behalf Of Ron Michael
Sent: Thursday, July 03, 2008 2:19 AM
To: rlearner309; Peter Dalgaard
Subject: Re: [R] A regression problem using dummy variables

"which group contrasts you want to look at" can you clarify me on that statement? mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Thu 03 Jul 2008 - 14:35:06 GMT

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