[R] Testing equality of regression model on multiple groups

David Winsemius dwinsemius at comcast.net
Fri Dec 18 14:30:13 CET 2009

On Dec 17, 2009, at 5:14 PM, Clara Yuan wrote:

> Hello,

> (Also, why are the coefficients renamed to t.L, t.Q, etc instead of  
> t.1, t.2?)

You have coded your t variable as an ordered factor.


if you do not want the linear, quadratic, cubic coefficients for the  
polynomial contrasts, then remove the ordering with:

t <- factor(t, is.ordered=FALSE)

... and rerun the analysis.


> What am I missing?
> Thanks for the help,
> Clara
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT

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