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

R## R Problem Overview

Suppose you are using `R`

and have data stored in a data frame, `M`

. Then I know that

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

will automatically fit a model where `Y`

is the dependent variables and all other columns of `M`

are the predictors. Is there an analogously simple way to additionally include every two way interaction?

## R Solutions

## Solution 1 - R

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.