[R-sig-ME] new R user struggling with error and convergence issues

[Ben Bolker]

It is admittedly hard to increase the "maxstephalfit" parameter, but
part of the reason we haven't put much effort into making it easier is
that in our experience it rarely helps.  Log-binomial models in
particular are tricky because the log link (i.e. the exponential
inverse-link) doesn't naturally constrain the response to the allowed
range of (0,1), so these models are hard to fit (the same applies to
inverse-link Gamma models).  The bigger your data set, the more likely
you are to run into cases where the predicted value is >1.  We could
admittedly do a much better job giving useful warnings about when and
where this problem occurred, and (more controversially) allow users to
clamp the output of the inverse-link function to the allowable domain
...

library("lme4")
set.seed(101)
dd <- data.frame(x=seq(-4,4,length=500),
                 f=sample(letters[1:10],size=500,replace=TRUE))
dd$y <- simulate(~x+(1|f),family=binomial,
                 newdata=dd,newparams=list(beta=c(0,1),theta=1))[[1]]
library("ggplot2")
ggplot(dd,aes(x,y,colour=f))+geom_point()+
    geom_smooth(method="glm",method.args=list(family=binomial))

m1 <- glmer(y~x+(1|f), dd, family=binomial)
m2 <- glmer(y~x+(1|f), dd, family=binomial(link="log"))  ## PIRLS
step-halving problem

On Mon, Feb 15, 2016 at 2:22 PM, Jennifer Yourkavitch via
R-sig-mixed-models <r-sig-mixed-models at r-project.org> wrote:
> Hello!
> I am fitting multilevel log-binomial models for a very large dataset (>53,000 observations), using glmer. I am getting this--  Error: (maxstephalfit) PIRLS step-halvings failed to reduce deviance in pwrssUpdate.
> And the model is not converging.
> I think that increasing the number of iterations may remediate the convergence issue. But I can’t find the right syntax for that online.
> Any advice re these two issues?
> Many thanks,
> Jennifer
>
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