This is an internal function for creating input matrices from formulas. It is currently used in some unit tests.
## S3 method for class 'formula_list'create_input_mats(object, input_data,...)
Arguments
object: An object of the appropriate class.
input_data: An object of class expanded_hesim_data returned by expand.hesim_data(). It is used to look for the variables needed to create an input matrix for use in a statistical models and the ID variables for indexing rows in the input matrix.