[R] LME correlation structures: user defined

[Steve Roberts]

Hi,

I noticed your old posts whilst tidying up my mailbox. I am struggling 
trying to understand the code to define new structures - part of the real 
work is hidden away in C code and I don't speak C very well. Have 
either of you successfully implemented any alternative structures? (At 
one stage I ws interested in trying Toeplitz forms, and now have a 
need for compound symmetry forms where the rho depends on a 
factor.) Have you anything beyond the source that might help? - for 
example a more richly commented example, or notes on what the C 
(and R)  functions actually do.

Regards,

Steve.




Date sent:      	Wed, 23 Mar 2005 10:56:46 +1100
To:             	"Michael Jerosch-Herold" <jeroschh at ohsu.edu>, R-help at stat.math.ethz.ch
From:           	Simon Blomberg <Simon.Blomberg at anu.edu.au>
Subject:        	Re: [R] LME correlation structures: user defined
Copies to:      	
> >Let me modify my question about user-defined covariance structures
> >for LME models: Can somebody tell me how I can see the code for the
> >definition of the correlation structures that come with the NLME
> >package. Specifically I like to see the code for the functions coef,
> >corMatrix, and intialize for any of the pre-defined correlation
> >structures, and use this as a template to define a new correlation
> >structure. So how do I see e.g. the code for the method initialize
> >for the correlation structure corExp or corARMA?
> 
> I'm interested in this too. Go to CRAN and download the source code
> for the nlme package. ungzip and untar it. Got to the R subdirectory.
> Inside that is a file called corStruct.R with all the method
> definitions for the built-in corStruct classes. Reading those should
> help.
> 
> Cheers,
> 
> Simon.
> 
> 
> >
> >thank you in advance!
> >
> >Michael Jerosch-Herold
> >
> >PS: Oh, and if somebody could still send me example code for a user
> >defined correlation structure I would much appreciate it, as my
> >previous requests for help have not yielded any response.
> >
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> 
> -- 
> Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
> Visiting Fellow
> School of Botany & Zoology
> The Australian National University
> Canberra ACT 0200
> Australia
> 
> T: +61 2 6125 8057  email: Simon.Blomberg at anu.edu.au
> F: +61 2 6125 5573
> 
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  Dr Steve Roberts 
  steve.roberts at manchester.ac.uk

Senior Lecturer in Medical Statistics,
CMMCH NHS Trust and University of Manchester Biostatistics Group,
0161 275 5192/5764 / 0161 276 5785