[R-sig-ME] Convergence warnings in lme4

[adam.hayward at ed.ac.uk]

Dear list users,

This is a general question, rather than a specific example of my data.  
I have recently upgraded my computer and to R ver 3.1.1 from 3.0.2.  
Models (glmer) which previously ran perfectly are now producing  
warning messages regarding failure to converge, for example:

Warning messages:
1: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv,  :
   Model failed to converge with max|grad| = 0.0238312 (tol = 0.001,  
component 13)
2: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv,  :
   Model failed to converge: degenerate  Hessian with 1 negative eigenvalues

and this is true with a range of optimizers. Running identical models  
on my old and new versions of R produces identical output (estimates,  
AIC etc) but the new version of lme4 produces the warnings.

My questions are thus (1) has lme4 recently been updated with  
significant changes in what constitutes acceptable convergence, and  
(2) can my models now be trusted?

Many thanks for any comments or help,

Adam



-- 
Adam Hayward
Post-Doctoral Research Associate
adhayward.wordpress.com

Institute of Evolutionary Biology
Ashworth Laboratories
King's Buildings
University of Edinburgh
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Edinburgh
EH9 3JT





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