ddiMatrix-class {Matrix} | R Documentation |

## Class "ddiMatrix" of Diagonal Numeric Matrices

### Description

The class `"ddiMatrix"`

of numerical diagonal matrices.
Note that diagonal matrices now extend `sparseMatrix`

, whereas
they did extend dense matrices earlier.

### Objects from the Class

Objects can be created by calls of the form `new("ddiMatrix", ...)`

but typically rather via `Diagonal`

.

### Slots

`x`

:numeric vector. For an `n \times n`

matrix, the `x`

slot is of length `n`

or `0`

,
depending on the `diag`

slot:

`diag`

:`"character"`

string, either `"U"`

or
`"N"`

where `"U"`

denotes unit-diagonal, i.e., identity
matrices.

`Dim`

,`Dimnames`

:matrix dimension and
`dimnames`

, see the `Matrix`

class
description.

### Extends

Class `"diagonalMatrix"`

, directly.
Class `"dMatrix"`

, directly.
Class `"sparseMatrix"`

, indirectly, see
`showClass("ddiMatrix")`

.

### Methods

- %*%
`signature(x = "ddiMatrix", y = "ddiMatrix")`

: ...

### See Also

Class `diagonalMatrix`

and function `Diagonal`

.

### Examples

```
(d2 <- Diagonal(x = c(10,1)))
str(d2)
## slightly larger in internal size:
str(as(d2, "sparseMatrix"))
M <- Matrix(cbind(1,2:4))
M %*% d2 #> `fast' multiplication
chol(d2) # trivial
stopifnot(is(cd2 <- chol(d2), "ddiMatrix"),
all.equal(cd2@x, c(sqrt(10),1)))
```

[Package

*Matrix* version 1.5-1

Index]