[S] linear and quadric effect of a predictor in linear regression

Zhaorong Jiao (z.jiao@qut.edu.au)
Tue, 06 Oct 1998 10:27:18 +1000 (EST)


Dear all, I am doing a linear regression using the function lm. There are
serveral preditors in the model. One I call it X. X only takes three
values: 0, 3 and 7 . How can I assess the linear and quadric effects of X
when using function lm. I have tried:
lm(reponse~X+other predictors, contrasts=list(X) and
lm(reponse~X+other predictors,contrasts=list(contrast(ordered(X))))
but none of them is successful. Can any one help me with this. Looking
forward to your answers. Thank you.

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:: Zhaorong(Jo) JIAO Ph: +61 7 3864 5267 / QUT::
:: School of Mathematics, GP. QUT, Fx: +61 7 3864 2310 \_.--._/ ::
:: PO Box 2434, Brisbane Q 4001, Australia Em: z.jiao@fsc.qut.edu.au V ::
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