Dear Douglas,

I also have had this problem of singular convergence (7) using the dredge
function at MuMIn package. I included verbose=TRUE in my global model and
ran again. However the message of singular convergence appeared again.

My analysis is about the determining factors on the local ant species. I
want to know if the local species richness is influenced by local factors
or factors that act at an immediately superior/lager scale.

I made a global model that encompasses factors acting at local scale and at
mesoscale. I considered surrogates of resource amount and resource
heterogeneity. I considered the absolute value of resource as local factor
and the average of these resource data as meso-factors.  I am following the
models averaging steps of Grueber et al. 2011.

global.model<-glmer(sarb~stree+numtree++stree.ave+numtree.ave+(1|park/transect),family="poisson")

Do you have some suggestions to solve it?

Thanks a lot in advance!

All the best,

Fernando


2012/2/9 Douglas Bates <bates@stat.wisc.edu>

> On Thu, Feb 9, 2012 at 11:08 AM, Toni Hernandez-Matias
> <ahmatias@gmail.com> wrote:
> > Dear all,
>
> > I am trying to fit a set of models with lmer function.
> > My aim is to investigate the relationship between the abundance of a
> mammal
> > species (count) and several environmental variables.
> > The sample size is 648, but the observations are not independent and the
> > random effect is nested: I have 10 study areas, within each area I
> > performed 6 transects. I have 9-10 observations in all transects. So an
> > example of a model with a single independent variable is:
> >
> mod05<-lmer(cagaders~E_arb_alt+(1|ter)+(1|ter:trans),data=conill,family=poisson)
>
> > When running this model I get the warning:
> > In mer_finalize(ans) : singular convergence (7)
>
> Try using verbose=TRUE to determine where the parameter values are
> going during the iterative optimization process.
>
> If your data could be made available, even in an anonymized form, we
> could check the model fit against other optimizers that may be more
> successful.
>
> > I don't see an apparent reason for this warning.
> > I would be very grateful if someone can help me to solve this problem and
> > to know wether the results in the fitted model are credible.
> >
> > Thank you very much in advance,
> >
> > Toni
> >
> > --
> > *********************************************************
> >
> > Antonio Hernandez Matias
> >
> > Departament de Biologia Animal (Vertebrats)
> > Facultat de Biologia
> > Universitat de Barcelona
> > Av. Diagonal, 645
> > Barcelona      08028
> > Spain
> > Telephone: +34-934035857
> > FAX: +34-934035740
> > e-mail: ahernandezmatias@ub.edu
> >
> > ***********************************************************
> >
> >        [[alternative HTML version deleted]]
> >
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>
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>



-- 
Fernando Augusto Schmidt
Lab. de Ecologia de Comunidades
PPG - Entomologia. Universidade Federal de Viçosa
Viçosa, MG - Brazil 36570-000
www.labecol.ufv.br
+55 35 92057632

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