[R] Forcing zero intercept in two predictor case - stat questionnot R question

[Leeds, Mark (IED)]

Hi john : I just checked it with a simple example before I saw your
email and that does work. Thanks and I apologize to you
and the list for the question.


-----Original Message-----
From: John Fox [mailto:jfox at mcmaster.ca] 
Sent: Wednesday, October 03, 2007 6:06 PM
To: Leeds, Mark (IED)
Cc: r-help at stat.math.ethz.ch
Subject: RE: [R] Forcing zero intercept in two predictor case - stat
questionnot R question

Dear Mark,

--------------------------------
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of Leeds, Mark (IED)
> Sent: Wednesday, October 03, 2007 5:49 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Forcing zero intercept in two predictor case - stat 
> questionnot R question
> 
> When one is doing simple regression and needs to force a zero 
> intercept ( for whatever reason. I realize it's a controversial issue 
> ), then subtracting the means of the left hand side and the right hand

> side from themselves does the trick. Does anyone know if there is a 
> similar trick when the RHS has two variables ? Thanks.

Yes, express all three variables as deviations from their means. (This
follows from the observation that the LS regression surface goes through
the centroid of the variables.)

Regards,
 John
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