[R] warnings when using binomial models and offset

[Joana Martelo]

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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