[R-sig-ME] Different within-group error correlation matrices per group

[Kevin Wright]

You might find the following links contain some useful information.

http://stackoverflow.com/questions/11819720/converting-repeated-measures-mixed-model-formula-from-sas-to-r

Factor-specific variances in R
https://rpubs.com/bbolker/6298

Harris wateruse
http://www.inside-r.org/packages/cran/agridat/docs/harris.wateruse


On Tue, Oct 27, 2015 at 8:57 PM, Luis Damiano <luiggi at gmail.com> wrote:

> Dear all,
>
> I am working with lme and I would like to have different within-group error
> correlation matrices per group (\Lambda_i in 5.1 from Pinheiro & Bates).
>
> Currently, my sentence looks like the following
>
> correlation = corCompSymm(form = ~ 1 | ind)
>
>
> which imposes the SC structure into the within-group error correlation
> matrix, marking the individuals by "ind".
>
> According to the following example in SAS given by an instructor, it is
> possible to estimate different within-group error correlation matrices per
> sex using the following sentences (see "group=gender" in fourth line):
>
> proc mixed  data=dental;
> >   class  child gender;
> >   model distance = gender gender*age / noint solution;
> >   repeated / group=gender subject=child;
> >   random intercept age / type=un subject=child g gcorr v vcorr;
> > run;
>
>
> I cannot figure out how to reproduce this in R. I took a look at the
> documentation as well as the first five chapters of Pinheiro & Bates (2000)
> without luck.
>
> Cheers!
>
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>
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>



-- 
Kevin Wright

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