dim                   package:base                   R Documentation

Dimensions of an Object

Description:

     Retrieve or set the dimension of an object.

Usage:

     dim(x)
     dim(x) <- value

Arguments:

       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).

Details:

     The functions 'dim' and 'dim<-' are generic.

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

Value:

     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.

References:

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

See Also:

     'ncol', 'nrow' and 'dimnames'.

Examples:

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

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

