make.formulas.saturated: Creates a formulas Argument
Description
This helper function creates a valid formulas object.
The formulas object is an argument to the mice::mice function.
It is a list of formulas that specifies the target variables and the predictors
by means of the standard ~ operator. In contrast to mice::make.formulas,
which creates main effects formulas, make.formulas.saturated
creates formulas including interaction effects.