singular convergence with lmer()

laurent stephane <laurent_step at ...> writes:

Dear all,

Using the latest CRAN version of lme4 
 I get the following warning from lmer() :

Warning message: 
In mer_finalize(ans) : singular convergence (7)

My model is not complicated and it works fine with SAS (if you are
interested in the details of my model see
forums.cirad.fr/logiciel-R/viewtopic.php?t=5071 )

What argument could I change in lmer() to overcome this warning ?

This warning emerges from the nlminb optimizer used in the guts
of lme4, and I don't think there's much you can do to suppress it
or change the behavior of nlminb to avoid it.  The best you could
do would be to use other packages (SAS, other versions of lme4 or
nlme, etc.) to see if the correct answer was achieved despite the
warning.

  Ben Bolker