Extract varFunc Formula

DESCRIPTION:

This method function extracts the formula associated with a varFunc object, in which covariates and grouping factors are specified.

USAGE:

formula(object) 

REQUIRED ARGUMENTS:

object
an object inheriting from class varFunc, representing a variance function structure.

VALUE:

if object has a formula attribute, its value is returned; else NULL is returned.

EXAMPLES:

formula(varPower(form = ~ fitted(.) | Sex))