| dimnames {base} | R Documentation |
Retrieve or set the dimnames of an object.
dimnames(x)
dimnames(x) <- value
x |
an R object, for example a matrix, array or data frame. |
value |
a possible value for |
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,
and a zero-length list to NULL. If value is a list
shorter than the number of dimensions, as from R 2.8.0 it is extended
with NULLs to the needed length.
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. The list can be named.
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.
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]]