I have to fit some data to a glm, family=poisson(link="log").
The response variables are X1, X2, X3 and X4.
I need an algorithm to fit the best possible model (by lowest AIC). All terms must be included plus the 64 possible combinations of interaction terms.
I'm currently using glmulti package, but that sometimes omits the terms X1, X2, X3 or X4, which must be included in my model.
Is there a way of forcing the glmulti package to always include these terms? ... Alternatively is there a way of constructing a loop that goes through the 64 possible models exhaustively and compares AIC?