[R-sig-ME] glmer warning messages using version 1.1.7

[Ben Bolker]

Sophia Kyriakou <sophia.kyriakou17 at ...> writes:

> 
> The bad news is that when I run the profList function I get an error
> message instead ...
> 

  I'm snipping most of the context from this thread, but just coming
back here to say I've posted a fairly thorough analysis of this issue
(along with pictures) at

http://rpubs.com/bbolker/proftest

  The answer there about the original question, "is it OK to 
ignore thse warnings?", is

tl;dr; yes. These are singular fits (due to a small number of levels of the
grouping variable), but that’s not actually the proximal problem. It turns
out that the second derivative of the random-effects std dev parameter is
quite small near zero (the MLE), making the estimated uncertainty in this
parameter very large and triggering warnings about scaling, etc etc, from
lme4. Plotting the profiles demonstrates (for the most part) that the level
of uncertainty is actually reasonable (upper 95% confidence interval around
2), just not well characterized by the local curvature at the MLE.