Message-ID: <20041128044907.VOUE1836.tomts16-srv.bellnexxia.net@JohnDesktop8300>
Date: 2004-11-28T04:49:08Z
From: John Fox
Subject: lm help: using lm when one point is known (not y intercept)
In-Reply-To: <41A94F59.6040702@wisc.edu>
Dear Seth,
You don't say which variable is the explanatory variable and which is the
response, but assuming that prob is to be regressed on effect, you can fit
lm(prob - 50 ~ I(effect + 37.25) - 1). That is you can shift the point
through which the regression is to go to the origin and then force the
regression through the origin.
I hope this helps,
John
--------------------------------
John Fox
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 stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Seth Imhoff
> Sent: Saturday, November 27, 2004 11:09 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] lm help: using lm when one point is known (not y
> intercept)
>
> Hello-
>
> My question is a short one. How can I specify a single point
> which through the fitted linear model has to go through? To
> illustrate my problem, the fit to following data must go
> through the point (-37.25(effect), 50(prob)). Note: you can
> ignore the label column.
>
> Effect Prob Label
>
> 1 -1143.75 7.142857 L
>
> 2 -572.75 21.428571 D
>
> 3 -223.75 35.714286 GL
>
> 4 123.25 50.000000 DG
>
> 5 359.75 64.285714 G
>
> 6 374.75 78.571429 DGL
>
> 7 821.75 92.857143 DL
>
>
> Thanks in advance!
>
> Seth Imhoff