On 2014-06-27 11:00, r-help-requ...@r-project.org wrote:
Date: Thu, 26 Jun 2014 15:12:08 +0200
> From: Carlos Bautista Le?n <carlosbautistal...@gmail.com>
> To: r-help@r-project.org
> Subject: [R] AICc in MuMIn package
Hello, I am modelling in glmmADMB count data
(I??m using a negative binomial distribution to avoid possitive
overdispersion) with four fixed and one random effect. I??m also using
MuMIn package to calculate the AICc and also to model averaging using
the function dredge. What I do not understand is why dredge calculates a
different value of the AICc and degrees of freedom than the function
AICc (please see bellow). Also the logLik changes (as expected).
>logLik (glmmadmb.Tot.Pr.nb) ---- 12 in model selection table
'log Lik.' -379.739 (df=6)
>logLik (glmmadmb.Tot.P.nb)------ 16 in model selection table
'log Lik.' -379.688 (df=7)
df AICc
glmmadmb.Tot.Pr.nb 6 772.8113----12 in model selection table
glmmadmb.Tot.P.nb 7 775.1825---- 16 in model selection table
Model selection table
(Int) Agr/100 Brd/100 Frs/100 HD/100 df logLik AICc delta
weight
12 0.90850 -10.570 17.08 1.4220 5 -397.992 806.9 0.00
0.713
16 1.10300 -10.470 17.39 -0.7603 1.5140 6 -397.730 808.8 1.87 0.280
Can anyone explain me why this happend? and which values are correct, those
from dredge function or those from AICc function?
Thank you very much in advace.
Carlos
your models 'glmmadmb.Tot.Pr.nb' and 'glmmadmb.Tot.P.nb' do not seem to
be identical to model '12' and '16', since 'df's do not match (5 and 6
vs 6 and 7). You can compare the model calls to see what differs them:
getCall( glmmadmb.Tot.Pr.nb )
getCall( <model.selection.table> , "12")
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