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dim(x), x a scalar, vector, matrix, array, structure, macro or GRAPH

Keywords: variables, null variables
dim(x) returns a vector containing the dimensions of x.  For example,
when x is a vector of length 10, dim(x) has value 10.  When x is a 5 by
7 matrix, dim(x) has value vector(5,7) and dim(x)[1] and dim(x)[2] are 5
and 7, respectively.  When x is an array with k dimensions, dim(x) is a
vector of length k.

When x is a macro or GRAPH variable, dim(x) is 1.

When x is a NULL variable, dim(x) is 0. This is a change from version
4.07 and earlier when dim(NULL) was NULL.

When x is a structure, dim(x) is a structure, each of whose components
is a structure with the same shape as x.  Suppose N is the largest
number of dimensions of any component of x or is 1 if all non-structure
components of x are NULL.  Then dim(x) has N components named 'dim1',
'dim2', ....  When xcomp is a non-NULL and non-structure component of x,
the corresponding component of dim(x)[j], that is, x$dimj, is
dim(xcomp)[j] when ndims(xcomp) <= j or 0 when ndims(xcomp) < j.  When
xcomp is NULL, the corresponding component of dim(x)[j] is 0.

  dim(4) is 1
  dim(run(6)) is 6
  dim(matrix(run(20),5)) is vector(5,4)
  dim(array(run(24),2,3,4)) is vector(2,3,4)
  dim(structure(run(6),structure(matrix(run(6),3),NULL)) is

See also topics length(), ndims(), 'structures', 'NULL'.

Gary Oehlert 2003-01-15