Hello,
Im trying to fit the following model:
Dependent variable: MAXDEPTH (the maximum depth reached by a penguin during
a given dive)
Fixed effects: SUCCESSMN (an index of the individual quality of a bird),
STUDYDAY (the day of the study, from -5 to 20, with 0=Dec 20), and the
interaction SUCCESSMN*STUDYDAY
Random effect: BIRD (the bird id, as each bird is performing several dives)
Using lmer with a poisson family, I got a huge amount of warning messages:
> reml.res <- lmer(MAXDEPTH~SUCCESSMN*STUDYDAY+(1|BIRD), family=poisson,
method=Laplace)
There were 50 or more warnings (use warnings() to see the first 50)
> warnings()
Warning messages:
1: non-integer x = 18.500000
2: non-integer x = 20.500000
3: non-integer x = 16.500000
Whereas it seems to be fine using the quasipoisson family:
> reml.res <- lmer(MAXDEPTH~SUCCESSMN*STUDYDAY+(1|BIRD),
family=quasipoisson(link="log"), method="Laplace")
> summary(reml.res)
Generalized linear mixed model fit using Laplace
Formula: MAXDEPTH ~ SUCCESSMN * STUDYDAY + (1 | BIRD)
Family: quasipoisson(log link)
AIC BIC logLik deviance
39581.16 39616.86 -19785.58 39571.16
Random effects:
Groups Name Variance Std.Dev.
BIRD (Intercept) 0.12383 0.3519
Residual 4.05206 2.0130
number of obs: 9324, groups: BIRD, 12
Fixed effects:
Estimate Std. Error t value
(Intercept) 3.6725244 0.1063978 34.517
SUCCESSMN 0.2978806 0.6824748 0.436
STUDYDAY 0.0069852 0.0021121 3.307
SUCCESSMN:STUDYDAY 0.0571982 0.0123831 4.619
Correlation of Fixed Effects:
(Intr) SUCCESSMN STUDYD
SUCCESSMN -0.276
STUDYDAY -0.099 -0.017
SUCCESSMN:S -0.075 -0.035 0.823
My first question is therefore: can someone tell me why I cant fit the
model with family=poisson?
Second, I would like to check the residuals but I really dont know how,
even after several hours searching the archives and other helps. I tried:
> residuals(reml.res)
Error: 'residuals' is not implemented yet
> resid(reml.res)
Error: 'resid' is not implemented yet
> names(reml.res)
NULL
> mcmcsamp(reml.res)
Error in .local(object, n, verbose, ...) :
mcmcsamp for GLMMs not yet implemented in supernodal representation
Im supposed to give a talk tomorrow and would be very grateful if someone
can help me
Im working with the following versions:
Package: Matrix
Version: 0.995-8
Date: 2006-03-21
Package: lme4
Version: 0.995-2
Date: 2006-01-17
Thank you!
Amélie
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