How to automatically include all 2-way interactions in a glm model in R

Question

Suppose you are using R and have data stored in a data frame, M. Then I know that

g <- glm(Y ~ ., data=M) 

wi

Answer 1

You can do two-way interactions simply using .*. and arbitrary n-way interactions writing .^n. formula(g) will tell you the expanded version of the formula in each of these cases.