Dears,

I encoutered the following message, when using lme4 :

Warning messages:
1: In mer_finalize(ans) :
  Cholmod warning 'not positive definite' at 
file:../Cholesky/t_cholmod_rowfac.c, line 432
2: In mer_finalize(ans) :
  Cholmod warning 'not positive definite' at 
file:../Cholesky/t_cholmod_rowfac.c, line 432
3: In mer_finalize(ans) : singular convergence (7)


I saw the same kind of message on your mailing list, but then I could 
not follow up the reply.

My model was:
 > ga1p<-glmer(A1P~T131006+typop*mr+(1|pop/fam), family= poisson)

The dataset is unbalanced:  there are 16 "pop", with a varying number of 
"fam" within pop. In one population, there is only one family.
The problem is related to T131006 (when omitted, glmer works). When I 
replace this covariate by another one, I have the same message, except 
in one particular case.


can anyone explain and help me?
Thanks in advance,
Agnès

-- 

Marie-Agnès Coutellec
UMR INRA-Agrocampus Ouest 985 ESE
Equipe Ecotoxicologie et Qualité des Milieux Aquatiques
65 rue de Saint-Brieuc - CS 84215
35042 Rennes cedex - FRANCE

tél.: +33(0)2 23 48 52 48
fax:  +33(0)2 23 48 54 40 


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