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Hi all, I was in a discussion with my advisor today, and the issue of "non-positive definite approximate variance-covariance" errors in R when using the lme() function arose. Depending on the varFunc specification that I use, I receive...

Hi all, I might be searching for something that doesn't exist -- but is there a way to obtain group-specific standard errors for random effect intercept estimates? I have hierarchical data grouped by "site," for which I've generated...

?Great -- that makes sense. Thank you! Jacob? On Feb 17, 2016 3:44 PM, "Douglas Bates" <bates at stat.wisc.edu> wrote: > The standard errors are for the fixed-effects parameters. The apVar > component includes approximate variances of the estimators...

Dear all, I am using lme() to run a mixed effects model on soil carbon observations, with fixed effects specified for latitude (continuous), and dominant genera of tree (factor with five levels), and random effects specified for site. The data...

Hi Thierry, Your suggestion is very helpful. Thanks! Jacob On Wed, Nov 18, 2015 at 11:46 AM, Thierry Onkelinx <thierry.onkelinx at inbo.be > wrote: > Dear Jacob, > > If you are willing to which to lme4, then you can use...

Dear Thierry, Thank you kindly for your advice. You were right in that the model is too complex for the dataset. I began examining the intervals of the coefficients and was getting "Non-positive definitive approximate variance-covariance" errors. Hopefully...

Dear all, I am currently trying to develop a predictive model of ecosystem carbon stocks for forests of Southeast Asia. The difficult part is that the dataset I've compiled (from published data in the peer-reviewed literature) only consists...