Dear list,
I am needing to extract the estimate of overdispersion (deviance / residual
degrees of freedom or c-hat) from multiple model objects - so they can then be
used to compare the extent of overdispersion among alternative models as well
as calculate qausi-AIC values. I have been unable to do this, despite
consulting a number of manuals and searching the R-help. I am imaging that in
theory it should be possible with some call to attr(), but i have so far had no
success.
An example model output would be:
> modeltest<-lmer(Coleodactylus_amazonicus_N~USD +
> (1|site),data=SFArray,family=poisson,method="Laplace",control=list(usePQL=FALSE,
> msVerbose=TRUE))
> summary(modeltest)
------------
Generalized linear mixed model fit using Laplace
Formula: Coleodactylus_amazonicus_N ~ USD + (1 | site)
Data: SFArray
Family: poisson(log link)
AIC BIC logLik deviance
75.94996 81.68603 -34.97498 69.94996
Random effects:
Groups Name Variance Std.Dev.
site (Intercept) 2.6076 1.6148
number of obs: 50, groups: site, 5
Estimated scale (compare to 1) 1.080798
------------
What I need is to extract this value (1.080798) from multiple lmer objects.
Has anyone any recommendations? I also need to do this for glm objects although
I suspect if someone was able to kindly point me in the right direction then
the solution is likely to be similar.
Very many thanks,
Toby Gardner
> sessionInfo()
Version 2.3.1 (2006-06-01)
i386-pc-mingw32
attached base packages:
[1] "datasets" "graphics" "grDevices" "methods" "stats" "utils"
"base"
other attached packages:
JGR iplots JavaGD lme4 Matrix lattice MASS
rJava
"1.4-7" "1.0-3" "0.3-4" "0.995-2" "0.995-15" "0.13-8" "7.2-27.1"
"0.4-6"
School of Environmental Sciences
University of East Anglia
Norwich, NR4 7TJ
United Kingdom
Email: [EMAIL PROTECTED]
Website: www.uea.ac.uk/~e387495
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