[R-sig-ME] "pdCompSymm" function in R package "nlme"
bbo|ker @end|ng |rom gm@||@com
Wed Oct 6 18:09:49 CEST 2021
Here are the available matrix classes available in nlme:
 "pdBlocked" "pdCompSymm" "pdConstruct" "pdDiag" "pdIdent"
 "pdLogChol" "pdMat" "pdMatrix" "pdNatural" "pdSymm"
Unfortunately, I don't think there's anything useful in there:
pdIdent is a multiple of the identity matrix, pdDiag is (heterogeneous)
I believe pdNatural, pdLogChol, pdSymm represent different
parameterizations for the general positive-definite ("unstructured")
So "equal correlations but heterogeneous variances" doesn't appear to
be an option.
The MCMCglmm package has more options.
glmmTMB offers a 'heterogeneous compound symmetric" but *not* (at
present) a *homogeneous compound symmetric" option (although that could
be achieved without too much difficulty by using the 'map' parameter to
set some parameters equal ...)
On 10/6/21 11:51 AM, Isaac Kookhyun Yoo wrote:
> Dear all,
> I am a graduate student. I have a question about pdCompSymm.
> pdCompSymm can be used for compound symmetry matrix only (All the variances
> are equal and all the covariances are equal.)
> Are there any functions for unequal variances or unequal covariances matrix?
> Thank you in advance.
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Dr. Benjamin Bolker
Professor, Mathematics & Statistics and Biology, McMaster University
Director, School of Computational Science and Engineering
Graduate chair, Mathematics & Statistics
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