dimnames {base} | R Documentation |

## Dimnames of an Object

### Description

Retrieve or set the dimnames of an object.

### Usage

dimnames(x)
dimnames(x) <- value

### Arguments

`x` |
an **R** object, for example a matrix, array or data frame. |

`value` |
a possible value for `dimnames(x)` : see
“Value”. |

### Details

The functions `dimnames`

and `dimnames<-`

are generic.

For an `array`

(and hence in particular, for a
`matrix`

), they retrieve or set the `dimnames`

attribute (see attributes) of the object. A list
`value`

can have names, and these will be used to label the
dimensions of the array where appropriate.

The replacement method for arrays/matrices coerces vector and factor
elements of `value`

to character, but does not dispatch methods for
`as.character`

. It coerces zero-length elements to `NULL`

.

Both have methods for data frames. The dimnames of a data frame are
its `row.names`

and its `names`

. For the
replacement method each component of `value`

will be coerced by
`as.character`

.

For a 1D matrix the `names`

are the same thing as the
(only) component of the `dimnames`

.

### Value

The dimnames of a matrix or array can be `NULL`

or a list of the
same length as `dim(x)`

. If a list, its components are either
`NULL`

or a character vector with positive length of the
appropriate dimension of `x`

.

For the `"data.frame"`

method both dimnames are character
vectors, and the rownames must contain no duplicates nor missing values.

### Note

Setting components of the dimnames, e.g.
`dimnames(A)[[1]] <- value`

is a common paradigm, but note that
it will not work if the value assigned is `NULL`

. Use
`rownames`

instead, or (as it does) manipulate the whole
dimnames list.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
*The New S Language*.
Wadsworth & Brooks/Cole.

### See Also

`rownames`

, `colnames`

;
`array`

, `matrix`

, `data.frame`

.

### Examples

## simple versions of rownames and colnames
## could be defined as follows
rownames0 <- function(x) dimnames(x)[[1]]
colnames0 <- function(x) dimnames(x)[[2]]

[Package

*base* version 2.5.0

Index]