I think this issue will be of interest to the list. It seems like a problem with nlme, and I was drawn into it because of a collaborator who encountered this issue in a simple experiment and wound up questioning the mixed model approach to his question.
The issue is that lme, when faced with certain numerically unstable problems, seems to produce incorrect answers (understandable), but without warnings (bad, in my opinion). I have attached a reproducible example. There is more information here: https://htmlpreview.github.io/?https://github.com/dushoff/scratch/blob/master/nlme.html and https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=16864. The first link shows my session information. Jonathan ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel