This function is a constructor for the
pdIdent class,
representing a multiple of the identity positive-definite matrix.
The matrix associated with
object is represented by 1
unrestricted parameter, given by the logarithm of the square-root of
the diagonal value. 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
pdIdent 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 value,
it is assumed to represent the unrestricted coefficient of the
underlying positive-definite matrix.
USAGE:
pdIdent(value, form, nam, data)
OPTIONAL 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
value. 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.
VALUE:
a
pdIdent object representing a multiple of the identity
positive-definite matrix, also inheriting from class
pdMat.
SEE ALSO:
,
,
EXAMPLES:
pd1 <- pdIdent(4 * diag(3), nam = c("A","B","C"))
pd1