symmetricMatrix-class {Matrix} | R Documentation |

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")`

.

`uplo`

: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.`factors`

:a list of matrix factorizations, also from the

`Matrix`

class.

Class `"Matrix"`

, directly.

- coerce
`signature(from = "ddiMatrix", to = "symmetricMatrix")`

: and many other coercion methods, some of which are particularly optimized.- dimnames
`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.- isSymmetric
`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"))`

.

`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.

`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
showClass("symmetricMatrix")
## The names of direct subclasses:
scl <- getClass("symmetricMatrix")@subclasses
directly <- sapply(lapply(scl, slot, "by"), length) == 0
names(scl)[directly]
## Methods -- applicaple to all subclasses above:
showMethods(classes = "symmetricMatrix")
```

[Package *Matrix* version 1.5-1 Index]