pdDiag {nlme} | R Documentation |
Diagonal Positive-Definite Matrix
Description
This function is a constructor for the pdDiag
class,
representing a diagonal positive-definite matrix. If the matrix
associated with object
is of dimension n
, it is
represented by n
unrestricted parameters, given by the logarithm
of the square-root of the diagonal values. When value
is
numeric(0)
, an uninitialized pdMat
object, a one-sided
formula, or a vector of character strings, object
is returned
as an uninitialized pdDiag
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
underlying positive-definite
matrix.
Usage
pdDiag(value, form, nam, data)
Arguments
value |
an optional initialization value, which can be any of the
following: a |
form |
an optional one-sided 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 positive-definite
matrix and unreplicated elements. This argument is ignored when
|
data |
an optional data frame in which to evaluate the variables
named in |
Value
a pdDiag
object representing a diagonal positive-definite
matrix, also inheriting from class pdMat
.
Author(s)
José Pinheiro 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
as.matrix.pdMat
,
coef.pdMat
,
pdClasses
,
matrix<-.pdMat
Examples
pd1 <- pdDiag(diag(1:3), nam = c("A","B","C"))
pd1