Extract pdMat Formula

DESCRIPTION:

This method function extracts the formula associated with a pdMat object, in which the column and row names are specified.

USAGE:

formula(object) 

REQUIRED ARGUMENTS:

object
an object inheriting from class pdMat, representing a positive definite matrix.

VALUE:

if object has a formula attribute, its value is returned, else NULL is returned. NOTE: Because factors may be present in formula(object), the pdMat object needs to have access to a data frame where the variables named in the formula can be evaluated, before it can resolve its row and column names from the formula.

SEE ALSO:

EXAMPLES:

pd1 <- pdSymm(~Sex*age) 
formula(pd1)