Re: [R] Warning messages in lmer function (package lme4)

From: Douglas Bates <dmbates_at_gmail.com>
Date: Mon 13 Jun 2005 - 23:36:37 EST

On 6/13/05, CENDOYA, Marķa Gabriela <gcendoya@balcarce.inta.gov.ar> wrote:
> Hi:
>
> I'm using function lmer from package lme4, and I get this message:
>
> " There were 12 warnings (use warnings() to see them)"
>
> So I checked them:
>
> Warnings 1 to 11 said:
>
> 1: optim returned message ERROR: ABNORMAL_TERMINATION_IN_LNSRCH
>
> in: "LMEoptimize<-"(`*tmp*`, value = structure(list(maxIter = 50, ...
>
>
>
> and Warning 12 said:
>
> 12: IRLS iterations for glmm did not converge in: lmer(Enfermo ~ Bloque +
> Trat * Var * dia + (1 | IDfruto), data = desinf, ...

> There was no error message in the call of lmer function, so:
>
> What do these warnings mean?
>
> Do these errors occur at earlier iterations but finally the model converges?

Yes. The PQL and Laplace methods for fitting generalized linear mixed models perform optimization of a criterion that is itself determined by an optimization problem. These warnings come from earlier iterations and are warnings.  

> Can the model I got be trusted?

Well George Box said that "All models are wrong" so in that sense you can't trust any fitted model. This type of model is difficult to fit and you should, as with all model fits, check the parameter values to see if they make sense to you.

You may want to try the same fit in a test build of R-devel, which will become R-2.2.0. In R-2.1.0 part of the optimization problem is performed by optim() and I have had some peculiar results from optim using method="L-BFGS-B". In constrained minimization I have had optim() declare convergence to a value on the boundary where the objective function was larger than at the starting point. I have added the function nlminb() to the development version of R-2.2.0 and use that for the constrained optimization problem in lmer(). I have found the results to be more reliable than those from optim().



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Jun 13 23:40:49 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:32:33 EST