pdMat                  package:nlme                  R Documentation

Positive-Definite Matrix

Description:

     This function gives an alternative way of constructing an object
     inheriting from the 'pdMat' class named in 'pdClass', or from
     'data.class(object)' if 'object' inherits from 'pdMat',  and is
     mostly used internally in other functions. See the documentation
     on the principal constructor function, generally with the same
     name as the 'pdMat' class of object.

Usage:

     pdMat(value, form, nam, data, pdClass)

Arguments:

   value: an optional initialization value, which can be any of the
          following: a 'pdMat' object, a positive-definite matrix, a
          one-sided linear formula (with variables separated by '+'), a
          vector of character strings, or a numeric vector. Defaults to
          'numeric(0)', corresponding to an uninitialized object.

    form: an optional one-sided linear formula specifying the
          row/column names for the matrix represented by 'object'.
          Because factors may be present in 'form', the formula needs
          to be evaluated on a data.frame to resolve the names it
          defines. This argument is ignored when 'value' is a one-sided
          formula. Defaults to 'NULL'.

     nam: an optional vector of character strings specifying the
          row/column names for the matrix represented by object. It
          must have  length equal to the dimension of the underlying
          positive-definite matrix and unreplicated elements. This
          argument is ignored when 'value' is a vector of character
          strings. Defaults to 'NULL'.

    data: an optional data frame in which to evaluate the variables
          named in 'value' and 'form'. It is used to obtain the levels
          for 'factors', which affect the dimensions and the row/column
          names of the underlying matrix. If 'NULL', no attempt is made
          to obtain information on  'factors' appearing in the
          formulas. Defaults to the parent frame from which the
          function was called.

 pdClass: an optional character string naming the 'pdMat' class to be
          assigned to the returned object. This argument will only be
          used when 'value' is not a 'pdMat'  object. Defaults to
          '"pdSymm"'.

Value:

     a 'pdMat' object representing a positive-definite matrix,
     inheriting from the class named in 'pdClass', or from
     'class(object)', if 'object' inherits from 'pdMat'.

Author(s):

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

References:

     Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S
     and S-PLUS", Springer.

See Also:

     'pdClasses',  'pdCompSymm', 'pdDiag', 'pdIdent', 'pdNatural',
     'pdSymm', 'reStruct', 'solve.pdMat',  'summary.pdMat'

Examples:

     pd1 <- pdMat(diag(1:4), pdClass = "pdDiag")
     pd1

