Convert pdMat Object to Natural Parameterization

DESCRIPTION:

This method function converts object to another pdMat 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. The exceptions are the pdSymm and pdBand classes (see the documentation on the appropriate asNatural method). 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., pdDiagNat is called for pdDiag objects). pdMat objects with constrained natural parameterization are represented by the variances and, when appropriate, the covariances of the positive-definite matrix they represent.

USAGE:

asNatural(object, unconstrained) 

REQUIRED ARGUMENTS:

object
an object inheriting from class pdMat, representing a positive-definite matrix, 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 (except for pdSymm and pdBand objects), else, if unconstrained = FALSE , a pdMat object parameterized according to the variances and covariances of the positive-definite matrix they represent - the class corresponding to these objects is obtained by appending the name Nat to the end of the original class of object.

SEE ALSO:

, , ,

EXAMPLES:

pd1 <- pdDiag(diag(1:3), form = ~age+age^2, data = Orthodont) 
asNatural(pd1, unc = F)