Create a Model Frame For Fitting a Tree Object

USAGE:

model.frame.tree(formula, ...) 

ARGUMENTS:

formula
the formula or other object defining what terms should be included in the model frame.

VALUE:

An object of class model.frame suitable for fitting a tree-based model. Called by tree and other functions for manipulating tree objects.

DETAILS:

This function is a method for the generic function for class tree. It can be invoked by calling for an object x of the appropriate class, or directly by calling regardless of the class of the object.