Hello-
I understand that log-likelihoods are bound to differ by constants, but if i estimate AIC for a set of simple nested linear models using the following 4 methods, shouldn't at least two of them produce the same ordering of models?

in R:
extractAIC
AIC

in S-PLUS:
AIC
n*log(deviance(mymodel)/n) + 2*p

I find it troubling that these methods all give me different answers as to the best model or even short set of models.

Thanks for your comments.

Alice Shelly

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