[R] AIC mathematical artefact or computation problem ?

lionel humbert humbert.lionel at courrier.uqam.ca
Thu Mar 23 17:28:29 CET 2006

Dear R user,

I have made many logistic regression (glm function) with a second order 
polynomial formula on a data set containing 440 observation of 96 
variables. I’ve made the plot of AIC versus the frequency 
(presence/observations) of each variable and I obtain a nearly perfect 
arch effect with a symmetric axe for a frequency of 0.5 . I obtain the 
same effect with deterministic data. Maybe I’ve miss something, but I 
have found nothing that could explain this in the theoretical 
calculation. Could it be due to the computation under R or AIC value is 
a function of frequency ?

Thanks for your consideration

Lionel Humbert
PhD candidate
Inter-University Forest Ecology Research Group
University of Quebec in Montreal

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