[R] (no subject)

[Francisco Vergara]

Dear Dr. Bates

I replied to your email before but apparently it didn't make it so I am 
replying again.  I would really appreciate if you could send me an example 
on how you suggest to build a cell means model for fixed effects using the 
NLME library.  I am not sure whether you suggest to create a separate factor 
for each unique combination of levels of a factor or whether you suggest to 
create a factor for each level of the original factors.  Wouldn’t the first 
case generate collinearity problems under some situations?

Many thanks again for your help

Francisco


>From: Douglas Bates <bates at stat.wisc.edu>
>To: "Francisco Vergara" <gerifalte28 at hotmail.com>
>Subject: Re: [R] (no subject)
>Date: 08 Oct 2003 19:21:13 -0500
>
>"Francisco Vergara" <gerifalte28 at hotmail.com> writes:
>
> > I want to specify the contrasts to build a cell means model on LME
> > when there are several fixed effect  as factors in the model and also
> > interactions between them.  Can anybody give me a hint on how to do
> > accomplish this? How can I override the default "Contr.Treatment" for
> > linear models?  I tried removing the intercept but this will only give
> > me the mean values just for the first factor included in the model but
> > then will use "contrast treatment" for all the other factors.
>
>You can't do what you want to do by defining interactions.
>
>If you really want a cell means model then construct a new factor
>with one level for each unique combination of your fixed factors and
>use this constructed factor and - 1 in the formula.
>
>That's what a cell means model is.  There is one parameter for each
>unique combination of factor levels from the original design.
>
>Let me know if this answer is too vague and I will provide an example.
>
>--
>Douglas Bates                            bates at stat.wisc.edu
>Statistics Department                    608/262-2598
>University of Wisconsin - Madison        http://www.stat.wisc.edu/~bates/

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