[R] RE: Simple NLME problem (I hope)

Ross Darnell r.darnell at uq.edu.au
Thu Mar 27 23:03:46 CET 2003

Date: Wed, 26 Mar 2003 17:35:27 +0000
From: "Vumani Dlamini" <dvumani at hotmail.com>
Subject: [R] Simple NLME problem (I hope)  
To: r-help at stat.math.ethz.ch
Message-ID: <F147zBdDA6VzpJxV0Hv00002661 at hotmail.com>
Content-Type: text/plain; format=flowed

"Vumani Dlamini" wrote:
>Dear R-Users:

>I would like to fit a multilevel model using LME such that the parameters 
>after fitting the multilevel in two separate groups and when I use the 
>complete data (with interactions between the grouping variable and the other 
>variables) set are comparable (or the same).

>The problem I am having currently is that I am not sure whether it is 
>possible to let the random error term to vary by group such that the models 
>are comparable. At present only one random error term is estimate and this 
>"sort of" distorts the parameter estimates for the fixed and other random 

>Looking forward to your help.

It may be that you want to use the "weights=varIdent(form=~1|groups)"
argument which will fit a variance for each level of the groups

Ross Darnell
School of Health and Rehabilitation Sciences
University of Queensland, Brisbane QLD 4067 AUSTRALIA
Email: <r.darnell at uq.edu.au>
Phone +61 7 3365 6087

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