R help - Nov 2018 - warnings when using binomial models and offset

Hello everyone

 

I'm trying to model fish capture success using length, velocity and group
composition as explanatory variables, density as an offset variable, and
fish.id. as random effect. I'm getting the follow warnings:

 

Model1<-glmer(capture~length+offset(density)+(1|fish.id),family=binomial,dat
a=cap)

 

Warning messages:

1: In checkConv(attr(opt, "derivs"), opt$par, ctrl =
control$checkConv,  :

  Model failed to converge with max|grad| = 0.260123 (tol = 0.001, component
1)

2: In checkConv(attr(opt, "derivs"), opt$par, ctrl =
control$checkConv,  :

  Model is nearly unidentifiable: very large eigenvalue

- Rescale variables?

 

 

-          I only get the warnings when I use length and group composition,
not with velocity.

-          I don't get any warning if I don't use the offset.

 

I've tried:

Model1<-glmer(capture~length+offset(log(density))+(1|fish.id.c),family=binom
ial(link="cloglog"),data=cap)

 

But still get the warning.

 

Any ideas of what might be the problem?

 

Many thanks!

 

 

Joana Martelo

 

 

 


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You should post this on the r-sig-mixed-models list, which is (obviously)
specifically concerned with mixed models, and where you are more likely to
find the expertise and help you seek.

Cheers,

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Nov 23, 2018 at 7:57 AM Joana Martelo <joanamartelo at gmail.com>
wrote:
> Hello everyone
>
>
>
> I'm trying to model fish capture success using length, velocity and
group
> composition as explanatory variables, density as an offset variable, and
> fish.id. as random effect. I'm getting the follow warnings:
>
>
>
> Model1<-glmer(capture~length+offset(density)+(1|fish.id
> ),family=binomial,dat
> a=cap)
>
>
>
> Warning messages:
>
> 1: In checkConv(attr(opt, "derivs"), opt$par, ctrl =
control$checkConv,  :
>
>   Model failed to converge with max|grad| = 0.260123 (tol = 0.001,
> component
> 1)
>
> 2: In checkConv(attr(opt, "derivs"), opt$par, ctrl =
control$checkConv,  :
>
>   Model is nearly unidentifiable: very large eigenvalue
>
> - Rescale variables?
>
>
>
>
>
> -          I only get the warnings when I use length and group composition,
> not with velocity.
>
> -          I don't get any warning if I don't use the offset.
>
>
>
> I've tried:
>
>
>
Model1<-glmer(capture~length+offset(log(density))+(1|fish.id.c),family=binom
> ial(link="cloglog"),data=cap)
>
>
>
> But still get the warning.
>
>
>
> Any ideas of what might be the problem?
>
>
>
> Many thanks!
>
>
>
>
>
> Joana Martelo
>
>
>
>
>
>
>
>
>         [[alternative HTML version deleted]]
>
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> PLEASE do read the posting guide
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>
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