Sometimes there can be terms in a formula that refer to a matrix instead of a single predictor. This function breaks up the matrix term into individual predictors to handle separately, as that is probably the intention of the user.
break_up_matrix_term(formula, data)
A list
containing the expanded formula
and the expanded
data.frame
.
A formula
for a valid model.
The original data.frame
with a matrix as predictor.