

   AArrrraayy EExxtteennttss

        dim(x)
        dim(x) <- values

   VVaalluuee::

        These generic functions retrieve the vector of extents
        of the array `x'.  The second form above is used to
        shape a nvector `x' as an array by specifying its
        extents `values'.

   SSeeee AAllssoo::

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

   EExxaammpplleess::

        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]

