dim {base}R Documentation

Dimensions of an Object


Retrieve or set the dimension of an object.


dim(x) <- value


x an R object, for example a matrix, array or data frame.
value For the default method, either NULL or a numeric vector, which is coerced to integer (by truncation).


The functions dim and dim<- are generic.

dim has a method for data.frames, which returns the lengths of the row.names attribute of x and of x (as the numbers of rows and columns respectively).

These functions are primitive, so argument names are ignored (but this might not be true of their methods).


For an array (and hence in particular, for a matrix) dim retrieves the dim attribute of the object. It is NULL or a vector of mode integer.

The replacement method changes the "dim" attribute (provided the new value is compatible) and removes any "dimnames" and "names" attributes.


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

See Also

ncol, nrow and dimnames.


x <- 1:12 ; dim(x) <- c(3,4)

# simple versions of nrow and ncol could be defined as follows
nrow0 <- function(x) dim(x)[1]
ncol0 <- function(x) dim(x)[2]

[Package base version 2.10.1 Index]