Convert varFunc Object to Natural Parameterization

DESCRIPTION:

This method function converts object to another varFunc object represented in a natural parameterization. If unconstrained is set to TRUE, the natural unconstrained parameterization used is the same as the one used for object, which is returned unchanged. If unconstrained is set to FALSE, a constrained natural parameterization is used to represent the object. In this case, a constructor with the name Nat appended to the end of the original object constructor is called (e.g., varPowerNat is called for varPower objects). varFunc objects with constrained natural parameterization are represented by the coefficients returned by coef(object, uncons = FALSE).

USAGE:

asNatural(object, unconstrained) 

REQUIRED ARGUMENTS:

object
an object inheriting from class varFunc, representing a variance function structure, whose representation is to be converted to a natural parameterization.

OPTIONAL ARGUMENTS:

unconstrained
an optional logical value indicating whether the natural parameterization should be unconstrained. Defaults to TRUE.

VALUE:

If unconstrained = TRUE, object is returned unchanged, else, if unconstrained = FALSE, a varFunc object parameterized according to the constrained coefficients corresponding to object - the class corresponding to these objects is obtained by appending the name Nat to the end of the original class of object.

EXAMPLES:

vf1 <- varConstPower(2, 0.5, form = ~age) 
vf1 <- initialize(vf1, data = Orthodont) 
asNatural(vf1, unc = F)