\HeaderA{pdBlocked}{Positive-Definite Block Diagonal Matrix}{pdBlocked}
\keyword{models}{pdBlocked}
\begin{Description}\relax
This function is a constructor for the \code{pdBlocked} class,
representing a positive-definite block-diagonal matrix. Each
block-diagonal element of the underlying  matrix is itself a
positive-definite matrix and is represented internally as an
individual \code{pdMat} object. When \code{value} is
\code{numeric(0)}, a list of uninitialized \code{pdMat} objects, a
list of one-sided formulas, or a list of vectors 
of character strings,  \code{object} is returned
as an uninitialized \code{pdBlocked} object (with just some of its
attributes and its class defined) and needs to have its coefficients
assigned later, generally using the \code{coef} or \code{matrix} replacement
functions. If \code{value} is a list of  initialized \code{pdMat}
objects, \code{object} will be constructed from the list obtained by
applying \code{as.matrix} to each of the \code{pdMat} elements of
\code{value}. Finally, if \code{value} is a list of numeric vectors,
they are assumed to represent the unrestricted coefficients
of the block-diagonal elements of the  underlying positive-definite
matrix.
\end{Description}
\begin{Usage}
\begin{verbatim}
pdBlocked(value, form, nam, data, pdClass)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{value}] an optional list with elements to be used as the
\code{value} argument to other \code{pdMat} constructors. These
include: \code{pdMat} objects, positive-definite
matrices, one-sided linear formulas, vectors of character strings, or
numeric vectors. All elements in the list must be similar (e.g. all
one-sided formulas, or all numeric vectors). Defaults to
\code{numeric(0)}, corresponding to an uninitialized object.
\item[\code{form}] an optional list of one-sided linear formulas specifying the
row/column names for the block-diagonal elements of the matrix
represented by \code{object}. Because factors may be present in
\code{form}, the formulas needs to be evaluated on a data.frame to
resolve the names they define. This argument is ignored when
\code{value} is a list of one-sided formulas. Defaults to \code{NULL}.
\item[\code{nam}] an optional list of vector of character strings specifying the
row/column names for the block-diagonal elements of the matrix
represented by object. Each of its components must have  
length equal to the dimension of the corresponding block-diagonal
element and unreplicated elements. This argument is ignored when 
\code{value} is a list of vector of character strings. Defaults to 
\code{NULL}.
\item[\code{data}] an optional data frame in which to evaluate the variables
named in \code{value} and \code{form}. It is used to
obtain the levels for \code{factors}, which affect the
dimensions and the row/column names of the underlying matrix. If
\code{NULL}, no attempt is made to obtain information on any
\code{factors} appearing in the formulas. Defaults to the parent
frame from which the function was called.
\item[\code{pdClass}] an optional vector of character strings naming the
\code{pdMat} classes to be assigned to the individual blocks in the
underlying matrix. If a single class is specified, it is used for all
block-diagonal elements. This argument will only be used when
\code{value} is missing, or its elements are not \code{pdMat}
objects. Defaults to \code{"pdSymm"}.
\end{ldescription}
\end{Arguments}
\begin{Value}
a \code{pdBlocked} object representing a positive-definite
block-diagonal matrix, also inheriting from class \code{pdMat}.
\end{Value}
\begin{Author}\relax
Jose Pinheiro \email{Jose.Pinheiro@pharma.novartis.com} and Douglas Bates \email{bates@stat.wisc.edu}
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{as.matrix.pdMat}{as.matrix.pdMat}}, \code{\LinkA{coef.pdMat}{coef.pdMat}},
\code{\LinkA{matrix<\Rdash.pdMat}{matrix<.Rdash..pdMat}}
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
pd1 <- pdBlocked(list(diag(1:2), diag(c(0.1, 0.2, 0.3))),
                 nam = list(c("A","B"), c("a1", "a2", "a3")))
pd1
\end{ExampleCode}
\end{Examples}

