pdFactor.reStruct            package:nlme            R Documentation

Extract Square-Root Factor from Components of an reStruct Object

Description:

     This method function extracts square-root factors of the
     positive-definite matrices corresponding to the 'pdMat' elements
     of 'object'.

Usage:

     ## S3 method for class 'reStruct':
     pdFactor(object)

Arguments:

  object: an object inheriting from class 'reStruct', representing a
          random effects structure and consisting of a list of 'pdMat'
          objects.

Value:

     a vector with square-root factors of the positive-definite
     matrices corresponding to the elements of 'object' stacked
     column-wise.

Note:

     This function is used intensively in optimization algorithms and
     its value is returned as a vector for efficiency reasons. The
     'pdMatrix' function can be used to obtain square-root factors in
     matrix form.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

See Also:

     'pdMatrix.reStruct', 'pdFactor.pdMat'

Examples:

     data(Orthodont)
     rs1 <- reStruct(pdSymm(diag(3), ~age+Sex, data = Orthodont))
     pdFactor(rs1)

