Extract varFunc Covariate

DESCRIPTION:

This method function extracts the covariate(s) associated with the variance function represented by object, if any is present.

USAGE:

getCovariate(object) 

REQUIRED ARGUMENTS:

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

VALUE:

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

SEE ALSO:

EXAMPLES:

vf1 <- varPower(1.1, form = ~age) 
covariate(vf1) <- Orthodont[["age"]] 
getCovariate(vf1)