TsparseMatrix-class {Matrix} | R Documentation |

## Class "TsparseMatrix" of Sparse Matrices in Triplet Form

### Description

The `"TsparseMatrix"`

class is the virtual class of
all sparse matrices coded in triplet form. Since it is a virtual class,
no objects may be created from it. See
`showClass("TsparseMatrix")`

for its subclasses.

### Slots

`Dim`

, `Dimnames`

:from the `"Matrix"`

class,

`i`

:Object of class `"integer"`

- the row indices
of non-zero entries *in 0-base*, i.e., must be in
`0:(nrow(.)-1)`

.

`j`

:Object of class `"integer"`

- the column
indices of non-zero entries. Must be the same length as slot
`i`

and *0-based* as well, i.e., in
`0:(ncol(.)-1)`

. For numeric Tsparse matrices, `(i,j)`

pairs can occur more than once, see `dgTMatrix`

.

### Extends

Class `"sparseMatrix"`

, directly.
Class `"Matrix"`

, by class `"sparseMatrix"`

.

### Methods

Extraction (`"["`

) methods, see
`[-methods`

.

### Note

Most operations with sparse matrices are performed using the
compressed, column-oriented or `CsparseMatrix`

representation. The triplet representation is convenient for
creating a sparse matrix or for reading and writing such
matrices. Once it is created, however, the matrix is generally
coerced to a `CsparseMatrix`

for further
operations.

Note that all `new(.)`

, `spMatrix`

and
`sparseMatrix(*, repr="T")`

constructors
for `"TsparseMatrix"`

classes implicitly add (i.e., “sum up”)
`x_k`

's that belong to identical `(i_k, j_k)`

pairs, see, the
example below, or also `"dgTMatrix"`

.

For convenience, methods for some operations such as `%*%`

and `crossprod`

are defined for
`TsparseMatrix`

objects. These methods simply
coerce the `TsparseMatrix`

object to a
`CsparseMatrix`

object then perform the
operation.

### See Also

its superclass, `sparseMatrix`

, and the
`dgTMatrix`

class, for the links to other classes.

### Examples

```
showClass("TsparseMatrix")
## or just the subclasses' names
names(getClass("TsparseMatrix")@subclasses)
T3 <- spMatrix(3,4, i=c(1,3:1), j=c(2,4:2), x=1:4)
T3 # only 3 non-zero entries, 5 = 1+4 !
```

[Package

*Matrix* version 1.5-1

Index]