\name{dsCMatrix-class}
\title{Numeric Symmetric Sparse (column compressed) Matrices}
\docType{class}
\alias{dsCMatrix-class}
\alias{dsTMatrix-class}
%
\alias{solve,dsCMatrix,dsparseMatrix-method}
\alias{solve,dsCMatrix,matrix-method}
\alias{solve,dsCMatrix,numeric-method}
\alias{solve,dsCMatrix,ddenseMatrix-method}
\alias{chol,dsCMatrix,missing-method}
\alias{chol,dsCMatrix,logical-method}
\alias{t,dsCMatrix-method}
\alias{t,dsTMatrix-method}
\alias{coerce,dgeMatrix,dsCMatrix-method}
\alias{coerce,dgeMatrix,dsTMatrix-method}
\alias{coerce,dsCMatrix,dgCMatrix-method}
\alias{coerce,dsCMatrix,dgTMatrix-method}
\alias{coerce,dsCMatrix,dgeMatrix-method}
\alias{coerce,dsCMatrix,dsRMatrix-method}
\alias{coerce,dsCMatrix,dsTMatrix-method}
\alias{coerce,dsCMatrix,dsyMatrix-method}
\alias{coerce,dsCMatrix,lsCMatrix-method}
\alias{coerce,dsCMatrix,generalMatrix-method}
\alias{coerce,dsCMatrix,matrix-method}
\alias{coerce,dsCMatrix,nsCMatrix-method}
\alias{coerce,dsTMatrix,dgTMatrix-method}
\alias{coerce,dsTMatrix,dgeMatrix-method}
\alias{coerce,dsTMatrix,dsCMatrix-method}
\alias{coerce,dsTMatrix,dsyMatrix-method}
\alias{coerce,dsTMatrix,lsTMatrix-method}
\alias{coerce,dsTMatrix,matrix-method}
\alias{coerce,dsyMatrix,dsCMatrix-method}
\alias{coerce,dsyMatrix,dsTMatrix-method}
\alias{coerce,dtCMatrix,dtRMatrix-method}
\alias{coerce,matrix,dsCMatrix-method}
\alias{coerce,matrix,dsTMatrix-method}
\alias{coerce,graphNEL,dsCMatrix-method}
\alias{determinant,dsCMatrix,missing-method}
\alias{determinant,dsCMatrix,logical-method}
\alias{image,dsCMatrix-method}
\description{The \code{dsCMatrix} class is a class of symmetric, sparse
numeric matrices in the compressed, column-oriented format. In this
implementation the non-zero elements in the columns are sorted into
increasing row order.\cr
The \code{dsTMatrix} class is the class of
symmetric, sparse numeric matrices in triplet format.
}
\section{Objects from the Class}{
Objects can be created by calls of the form \code{new("dsCMatrix",
...)} or \code{new("dsTMatrix", ...)} or (for \code{dsCMatrix}) also
automatically from \code{\link{Matrix}(.)}.
}
\section{Slots}{
\describe{
\item{\code{uplo}:}{A character object indicating if the upper
triangle (\code{"U"} or \code{"u"}) or the lower triangle
(\code{"L"} or \code{"l"}) is stored.}
\item{\code{i}:}{Object of class \code{"integer"} of length nnZ
(\emph{half} number of non-zero elements). These are the row
numbers for each non-zero element in the lower triangle of the matrix.}
\item{\code{p}:}{(only in class \code{"dsCMatrix"}:) Object of class
\code{"integer"} of pointers, one for each column, to the initial
(zero-based) index of elements in the column.}
\item{\code{j}:}{(only in class \code{"dsTMatrix"}:) Object of
class \code{"integer"} of length nnZ (as \code{i}). These are the
column numbers for each non-zero element in the lower triangle of
the matrix.}
\item{\code{x}:}{Object of class \code{"numeric"} of length nnZ --
the non-zero elements of the matrix (to be duplicated for full matrix).}
\item{\code{factors}:}{Object of class \code{"list"} - a list
of factorizations of the matrix. }
\item{\code{Dim}:}{Object of class \code{"integer"} - the dimensions
of the matrix - must be an integer vector with exactly two
non-negative values.}
}
}
\section{Extends}{
Both classes extend classes and \code{\linkS4class{symmetricMatrix}}
\code{\linkS4class{dsparseMatrix}} directly;
\code{dsCMatrix} further directly extends
\code{\linkS4class{CsparseMatrix}}, where
\code{dsTMatrix} does \code{\linkS4class{TsparseMatrix}}.
}
\section{Methods}{
\describe{
\item{solve}{\code{signature(a = "dsCMatrix", b = "dsparseMatrix")}: Solve
a linear system of equations defined by \code{x} using a Cholesky
decomposition. All steps will be based on \emph{sparse}
representations.}
\item{solve}{\code{signature(a = "dsCMatrix", b = "matrix")}: Solve
a linear system of equations defined by \code{x} using a Cholesky
decomposition.}
\item{chol}{\code{signature(x = "dsCMatrix", pivot = "logical")}:
Returns (and stores) the Cholesky decomposition of the matrix
\code{x}. If \code{pivot} is \code{TRUE} (the default) Metis is
used to create a reordering of the rows and columns of \code{x} so
as to minimize fill-in.}
\item{Cholesky}{\code{signature(A = "dsCMatrix",...)}:
Computes more flexibly Cholesky decompositions,
see \code{\link{Cholesky}}.}
\item{determinant}{\code{signature(x = "dsCMatrix", logarithm =
"missing")}: Evaluate the determinant of \code{x} on the
logarithm scale. This creates and stores the Cholesky factorization.}
\item{determinant}{\code{signature(x = "dsCMatrix", logarithm =
"logical")}: Evaluate the determinant of \code{x} on the
logarithm scale or not, according to the \code{logarithm}
argument. This creates and stores the Cholesky factorization.}
\item{t}{\code{signature(x = "dsCMatrix")}: Transpose. Because
\code{x} is symmetric this has no effect.}
\item{t}{\code{signature(x = "dsTMatrix")}: Transpose. For the
\code{dsTMatrix} class the row and column indices are interchanged
so that a matrix for which the upper triangle is stored produces a
matrix for which the lower triangle is stored and vice versa.}
\item{coerce}{\code{signature(from = "dsCMatrix", to = "dgTMatrix")}}
\item{coerce}{\code{signature(from = "dsCMatrix", to = "dgeMatrix")}}
\item{coerce}{\code{signature(from = "dsCMatrix", to = "matrix")}}
\item{coerce}{\code{signature(from = "dsTMatrix", to = "dgeMatrix")}}
\item{coerce}{\code{signature(from = "dsTMatrix", to = "dsCMatrix")}}
\item{coerce}{\code{signature(from = "dsTMatrix", to = "dsyMatrix")}}
\item{coerce}{\code{signature(from = "dsTMatrix", to = "matrix")}}
}
}
%\references{}
%\author{}
%\note{}
\seealso{
Classes \code{\linkS4class{dgCMatrix}}, \code{\linkS4class{dgTMatrix}},
\code{\linkS4class{dgeMatrix}} and those mentioned above.
}
\examples{
## First a "dgCMatrix"
mm <- Matrix(toeplitz(c(10, 0, 1, 0, 3)), sparse = TRUE)
mT <- as(mm, "dgTMatrix")
(symM <- as(mT, "dsCMatrix"))
str(symM)
sym2 <- as(symM, "TsparseMatrix")
stopifnot(class(sym2) == "dsTMatrix",
identical(sym2[1,], symM[1,]),
identical(sym2[,2], symM[,2]))
}
\keyword{classes}
\keyword{algebra}