[R-sig-ME] nlme package, fixing variance.covariance matrix of residuals
Viechtbauer Wolfgang (SP)
wolfgang.viechtbauer at maastrichtuniversity.nl
Thu Aug 17 23:13:42 CEST 2017
To address the original question directly: No, this isn't possible with nlme (you can only specify known variances, not an entire var-cox matrix).
From: R-sig-mixed-models [mailto:r-sig-mixed-models-bounces at r-project.org] On Behalf Of Phillip Alday
Sent: Thursday, August 17, 2017 22:51
To: Wölwer, Anna-Lena; r-sig-mixed-models at r-project.org
Subject: Re: [R-sig-ME] nlme package, fixing variance.covariance matrix of residuals
This is an indirect (non)-answer, but Wolfgang Viechtbauer has a nice
comparison of lme and rma in the metafor online documentation:
It might be possible to figure out your problem from that -- and if you
do, please 'self-answer' on the list to document it for other users!
On 08/17/2017 07:09 PM, Wölwer, Anna-Lena wrote:
> Dear R team,
> I would like to do a multivariate meta-analysis in R using the nlme package. In meta-analysis I fix the residuals to known sampling errors. As I do a multivariate analysis, I have a variance-covariance matrix of sampling errors. Unfortunately, via varFixed I can only fix a vector of sampling errors and no matrix.
> In the R package metafor using the rma.mv function I can insert the variance-covariance matrix in the function. I would like to do the same with lme from the nlme package as nlme provides more flexibility for my model.
> Do you now any possibility of doing so in nlme? Are there any changes planned to incorporate this feature?
> Best wishes, I am looking forward to your feedback
> Anna-Lena W�lwer
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