[R] bVar slot of lmer objects and standard errors

[Ulrich Keller]

Hello,

I am looking for a way to obtain standard errors for emprirical Bayes estimates of a model fitted with lmer (like the ones plotted on page 14 of the document available at http://www.eric.ed.gov/ERICDocs/data/ericdocs2/content_storage_01/0000000b/80/2b/b3/94.pdf). Harold Doran mentioned (http://tolstoy.newcastle.edu.au/~rking/R/help/05/08/10638.html) that  the posterior modes' variances can be found in the bVar slot of lmer objects. However, when I fit e.g. this model:

lmertest1<-lmer(mathtot~1+(m_escs_c|schoolid),hlmframe)

then lmertest1 at bVar$schoolid is a three-dimensional array with dimensions (2,2,28). The factor schoolid has 28 levels, and there are random effects for the intercept and m_escs_c, but what does the third dimension correspond to? In other words, what are the contents of bVar, and how can I use them to get standard errors?

Thanks in advance for your answers and Merry Christmas,

Uli Keller