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 <[EMAIL PROTECTED]> To: "Francisco Vergara" <[EMAIL PROTECTED]> Subject: Re: [R] (no subject) Date: 08 Oct 2003 19:21:13 -0500
"Francisco Vergara" <[EMAIL PROTECTED]> 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 [EMAIL PROTECTED] Statistics Department 608/262-2598 University of Wisconsin - Madison http://www.stat.wisc.edu/~bates/
_________________________________________________________________ See when your friends are online with MSN Messenger 6.0. Download it now
______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
