Re: [R] A regression problem using dummy variables

From: Ron Michael <>
Date: Thu, 03 Jul 2008 20:34:05 -0700 (PDT)

"V&R's MASS book" can you give the full name of that book

From: Bert Gunter <> Subject: RE: [R] A regression problem using dummy variables To:
Date: Thursday, 3 July, 2008, 9:21 PM

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

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