The R documentation for either does not shed much light. All that I can get from this link is that using either one should be fine. What I do not get is why they are not equal.
Fact: The stepwise regression function in R,
Interestingly, running a
lm() model and a
glm() 'null' model (only the intercept) on the 'mtcars' data set of R gives different results for
> null.glm = glm(mtcars$mpg~1) > null.lm = lm(mtcars$mpg~1) > AIC(null.glm)  208.7555 > AIC(null.lm)  208.7555 > extractAIC(null.glm)  1.0000 208.7555 > extractAIC(null.lm)  1.0000 115.9434
It is weird, given that both the models above are the same, and
AIC() gives the same results for both.
Can anyone throw some light on the issue?