[R-sig-ME] false convergence (8) with binary covariate (0, 1) but NOT if covariate is (no, yes)?
Paul Metzner
paul.metzner at gmail.com
Tue Mar 8 15:01:29 CET 2011
> a) Why is that so?
Is it possible that you coded the variable as an integer before and as a factor now? I'm not sure if lmer treats a two-level integer as a factor, but that might have been it.
> b) How can I fix the false convergence problem if my covariate has also a binary format?
You might try to apply sum contrasts, i.e., -1/2 and 1/2. Everybody please correct me if this is nonsense.
Best,
Paul
On 8 Mar 2011, at 14:25, Julia Sommerfeld wrote:
> Dear list,
>
> The false convergence warning message (8) seems to be a common problem in
> lmer. I've searched the archives to find a solution and found out that one
> approach would be standardizing my covariate to mean-center the data.
>
> However, what if the covariate itself (in this case SameMate) has a binary
> value (0,1)?
>
> After testing for the effect of the breeding success on site-fidelity (and
> finally understanding the summary output), I would like to account for the
> effect of breeding success (successfull=1, unsuccessfull=0) on mate-fidelity
> (mate-fidelity=1, no mate-fidelity=0).
>
> I.e. does the model including BreedSuc1 fits better than without it:
>
> fm<-lmer(SameMate~BreedSuc1+(1|Bird),family="binomial")
> fm1<-lmer(SameMate~1+(1|Bird),family="binomial")
>
> Both models get the warning message:
>
> In mer_finalize(ans) : false convergence (8)
>
> anova(fm,fm1)
> Data:
> Models:
> fm1: SameMate ~ 1 + (1 | Bird)
> fm: SameMate ~ BreedSuc1 + (1 | Bird)
> Df AIC BIC logLik Chisq Chi Df Pr(>Chisq)
> fm1 2 48.659 52.946 -22.330
> fm 3 50.342 56.771 -22.171 0.3174 1 0.5732
>
> Now the weird thing:
>
> I simply changed the coding of my covariate from "0,1" to "no, yes". Now,
> only model fm1 gets the false convergence message:
>
>> fm<-lmer(SameMate~BreedSuc1+(1|Bird),family="binomial")
>> fm1<-lmer(SameMate~1+(1|Bird),family="binomial")
> Warning message:
> In mer_finalize(ans) : false convergence (8)
>
> Data:
> Models:
> fm1: SameMate ~ 1 + (1 | Bird)
> fm: SameMate ~ BreedSuc1 + (1 | Bird)
> Df AIC BIC logLik Chisq Chi Df
> Pr(>Chisq)
> fm1 2 47.490 51.468 -21.745
> fm 3 54.096 60.063 -24.048 0 1 1
>
> a) Why is that so?
> b) How can I fix the false convergence problem if my covariate has also a
> binary format?
>
> I would highly appreciate suggestions and ideas.
>
> Cheers,
>
> Julia
>
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>
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