s.hatchcoltailmodel1.76<-lmer(nhatch1~sex+tlength+brithr+briventral+cond+weatherpc1+weatherpc1:briventral+weatherpc1:cond+(1|site/pair)+(1|year),family=poisson,na.action=na.omit,verbose=TRUE)

  0:     129.32699:  1.05525 0.617213 0.242091  2.11758 -0.0668442 0.00235620 0.00296124 0.000930340 -0.619141 0.622250 0.00267117 -0.537532
  1:     129.32699:  1.05525 0.617213 0.242091  2.11758 -0.0668442 0.00235620 0.00296124 0.000930340 -0.619141 0.622250 0.00267117 -0.537532

Mensajes de aviso perdidos
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) : false convergence (8)


   I thought it could be overparametrized, but in that case, why don't I get any error with the maximum model, which has much more parameters to estimate? 


   Thank you very much. Iker



________________________________
De: Douglas Bates <bates@stat.wisc.edu>

CC: "r-sig-mixed-models@r-project.org" <r-sig-mixed-models@r-project.org>
Enviado: domingo 24 de julio de 2011 19:06
Asunto: Re: [R-sig-ME] Cholmod warning


ote:

>    Dear list:

>    I am implementing a model with lmer in which the dependent variable is the number of chicks fledged by a number of barn swallow couples. I am using the simplification method, and have realized that the order in which different elements are introduced in the model has a great important, to the extent of making a "false convergence" warning message disappear. After doing all the simplification, I arrive to this model:

>    s.hatchcoltailmodel1.76<-lmer(nhatch1~sex+tlength+brithr+briventral+cond+weatherpc1+weatherpc1:briventral+weatherpc1:cond+(1|site/pair)+(1|year),family=poisson,na.action=na.omit)

>    This one, the LAST one (and the simplest) gives me this error message:

>    Mensajes de aviso perdidos
> 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) : false convergence (8)

>    No matter the order in which I write the elements.

>    I really cannot understand how it is possible that I have been able to make all the simplification from the maximal model (18 parameters), and after a long and careful process, exactly when I arrive to my minimal model (8 parameters and only 2 interactions) is when everything collapses. It is really annoying.

Add the verbose=TRUE option to see if you can determine which of the
parameters is going off to unusual values.  It is entirely possible
that your model is overparameterized.

>
>    Any suggestions, comments or ideas'll be much appreciated.
>
>    Thank you very much.
>
>
>   ________________________________________
>
>    Iker Vaquero-Alba
>    Centre for Ecology and Conservation
>    Daphne du Maurier Building
>    University of Exeter, Cornwall Campus
>    Treliever Road
>    TR10 9EZ Penryn
>    U.K.
>
>    http://biosciences.exeter.ac.uk/cec/staff/postgradresearch/ikervaquero-alba/
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>
>
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