dimnames {base}R Documentation

Dimnames of an Object


Retrieve or set the dimnames of an object.


dimnames(x) <- value


x an R object, for example a matrix, array or data frame.
value a possible value for dimnames(x): see “Value”.


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.


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.


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.


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.


## 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]