7.4 Practical Considerations

• Is it possible to identify all possible predictive interactions?

• Is it possible to evaluate all possible interactions?

• Should the interaction terms be created before or after the preprocessing part?

Only a fraction of all possible pairwise interactions contain relevant information.

With $p$ predictors we have $(p)(p-1)/2$ pairwise interaction terms.

Here is the difference in interaction effects before and after preprocessing: