pdSymm {nlme}  R Documentation 
This function is a constructor for the pdSymm
class,
representing a general positivedefinite matrix. If the matrix
associated with object
is of dimension n, it is
represented by n*(n+1)/2 unrestricted parameters,
using the matrixlogarithm parametrization described in Pinheiro and
Bates (1996). When value
is numeric(0)
, an uninitialized
pdMat
object, a onesided
formula, or a vector of character strings, object
is returned
as an uninitialized pdSymm
object (with just some of its
attributes and its class defined) and needs to have its coefficients
assigned later, generally using the coef
or matrix
replacement
functions. If value
is an initialized pdMat
object,
object
will be constructed from
as.matrix(value)
. Finally, if value
is a numeric vector,
it is assumed to represent the unrestricted coefficients of the
matrixlogarithm parametrization of the underlying positivedefinite
matrix.
pdSymm(value, form, nam, data)
value 
an optional initialization value, which can be any of the
following: a 
form 
an optional onesided linear formula specifying the
row/column names for the matrix represented by 
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 positivedefinite
matrix and unreplicated elements. This argument is ignored when

data 
an optional data frame in which to evaluate the variables
named in 
a pdSymm
object representing a general positivedefinite
matrix, also inheriting from class pdMat
.
JosÃ© Pinheiro and Douglas Bates bates@stat.wisc.edu
Pinheiro, J.C. and Bates., D.M. (1996) "Unconstrained Parametrizations for VarianceCovariance Matrices", Statistics and Computing, 6, 289296.
Pinheiro, J.C., and Bates, D.M. (2000) "MixedEffects Models in S and SPLUS", Springer.
as.matrix.pdMat
,
coef.pdMat
,
pdClasses
,
matrix<.pdMat
pd1 < pdSymm(diag(1:3), nam = c("A","B","C")) pd1