symmetricMatrix-class {Matrix}R Documentation

Virtual Class of Symmetric Matrices in Package Matrix


The virtual class of symmetric matrices, "symmetricMatrix", from the package Matrix contains numeric and logical, dense and sparse matrices, e.g., see the examples with the “actual” subclasses.

The main use is in methods (and C functions) that can deal with all symmetric matrices, and in as(*, "symmetricMatrix").



Object of class "character". Must be either "U", for upper triangular, and "L", for lower triangular.

Dim, Dimnames:

The dimension (a length-2 "integer") and corresponding names (or NULL), inherited from the Matrix, see there. See below, about storing only one of the two Dimnames components.


a list of matrix factorizations, also from the Matrix class.


Class "Matrix", directly.



signature(from = "ddiMatrix", to = "symmetricMatrix"): and many other coercion methods, some of which are particularly optimized.


signature(object = "symmetricMatrix"): returns symmetric dimnames, even when the Dimnames slot only has row or column names. This allows to save storage for large (typically sparse) symmetric matrices.


signature(object = "symmetricMatrix"): returns TRUE trivially.

There's a C function symmetricMatrix_validate() called by the internal validity checking functions, and also from getValidity(getClass("symmetricMatrix")).

Validity and dimnames

The validity checks do not require a symmetric Dimnames slot, so it can be list(NULL, <character>), e.g., for efficiency. However, dimnames() and other functions and methods should behave as if the dimnames were symmetric, i.e., with both list components identical.

See Also

isSymmetric which has efficient methods (isSymmetric-methods) for the Matrix classes. Classes triangularMatrix, and, e.g., dsyMatrix for numeric dense matrices, or lsCMatrix for a logical sparse matrix class.


## An example about the symmetric Dimnames:
sy <- sparseMatrix(i= c(2,4,3:5), j= c(4,7:5,5), x = 1:5, dims = c(7,7),
                   symmetric=TRUE, dimnames = list(NULL, letters[1:7]))
sy # shows symmetrical dimnames
sy@Dimnames  # internally only one part is stored
dimnames(sy) # both parts - as sy *is* symmetrical


## The names of direct subclasses:
scl <- getClass("symmetricMatrix")@subclasses
directly <- sapply(lapply(scl, slot, "by"), length) == 0

## Methods -- applicaple to all subclasses above:
showMethods(classes = "symmetricMatrix")

[Package Matrix version 1.2-17 Index]