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\name{triangularMatrix-class}
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\docType{class}
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\alias{triangularMatrix-class}
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\alias{coerce,triangularMatrix,symmetricMatrix-method}
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%
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\title{Virtual Class of Triangular Matrices in package:Matrix}
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\description{
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  The virtual class of triangular matrices,\code{"triangularMatrix"},
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  from the package \pkg{Matrix} contains numeric and logical, dense and
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  sparse matrices, e.g., see the examples.
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  The main use will be in methods (and C functions) that can deal with
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  all triangular matrices.
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}
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% \section{Objects from the Class}{A virtual Class: No objects may be created from it.}
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\section{Slots}{
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  \describe{
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    \item{\code{uplo}:}{String (of class \code{"character"}).  Must be
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      either "U", for upper triangular, and "L", for lower triangular.}
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    \item{\code{diag}:}{String (of class \code{"character"}).  Must be
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      either \code{"U"}, for unit triangular (diagonal is all ones), or
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      \code{"N"} for non-unit.  The diagonal elements are not
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      accessed internally when \code{diag} is \code{"U"}. For
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      \code{\linkS4class{denseMatrix}} classes, they need to be
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      allocated though, i.e., the length of the \code{x} slot does not
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      depend on \code{diag}.}
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    \item{\code{Dim}, \code{Dimnames}:}{The dimension (a length-2
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      \code{"integer"}) and corresponding names (or \code{NULL}),
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      inherited from the \code{\linkS4class{Matrix}}, see there.}
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  }
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}
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\section{Extends}{
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  Class \code{"Matrix"}, directly.
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}
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\section{Methods}{
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  There's a C function \code{triangularMatrix_validity()}
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  called by the internal validity checking functions.
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  Currently, \code{\link{Schur}}, \code{\link{isSymmetric}} and
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  \code{as()} (i.e. \code{\link{coerce}}) have methods with
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  \code{triangularMatrix} in their signature.
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}
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\seealso{
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  Classes \code{\linkS4class{symmetricMatrix}}, and, e.g.,
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  \code{\linkS4class{dtrMatrix}} for numeric \emph{dense} matrices, or
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  \code{\linkS4class{ltCMatrix}} for a logical \emph{sparse} matrix
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  subclass of \code{"triangularMatrix"}.
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}
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\examples{
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showClass("triangularMatrix")
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## The names of direct subclasses:
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scl <- getClass("triangularMatrix")@subclasses
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directly <- sapply(lapply(scl, slot, "by"), length) == 0
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names(scl)[directly]
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}
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\keyword{classes}