[R-sig-ME] lmer, poisson family and mcmcsamp

Amelie LESCROEL lescroel at cebc.cnrs.fr
Mon Feb 16 16:59:53 CET 2009

Dear all,

Could someone explain to me why summary(lmer.object) is giving z values 
and Pr(>|z|) when the lmer.object was fitted with family=poisson? I used 
to fit linear mixed models with family=gaussian and link="identity" or 
link="log", then used mcmcsamp() and HPDinterval() for computing 
"confidence" intervals and considered that a fixed effect was 
significant when the 95% HPD interval did not include zero. Now, with 
family=poisson, when I use mcmcsamp(), I get the following:

 > set.seed(101); mcmcfm1 <- mcmcsamp(fm1, n=10000)
Error in .local(object, n, verbose, ...) : Update not yet written

but I get z values and Pr(>|z|). Why is it so? Can we "trust" this 
probability for judging of the fixed effects significance? Would the 
mcmcsamp method be available soon for families other than gaussian?

Thanks in advance,


PS: When will lme4_1.0 be released? Many thanks to Douglas Bates for 
developing lme4 in interaction with users, and for sharing it. Please 
don't give up on making it available in R. lme4 is a wonderful tool 
which is helping me understanding penguin's foraging behaviour (and 
advanced stats!) as it is helping others in plant ecology or human 

 > sessionInfo()
R version 2.7.2 (2008-08-25)


attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base    

other attached packages:
[1] lme4_0.999375-28   Matrix_0.999375-17 lattice_0.17-17    

loaded via a namespace (and not attached):
[1] grid_2.7.2   gtools_2.5.0 tools_2.7.2

__________ Information from ESET Mail Security, version of virus signature database 3857 (20090216) __________

The message was checked by ESET Mail Security.

More information about the R-sig-mixed-models mailing list