1## Copyright (C) 2000, 2006, 2007, 2009 Paul Kienzle
3## This file is part of Octave.
5## Octave is free software; you can redistribute it and/or modify it
6## under the terms of the GNU General Public License as published by
7## the Free Software Foundation; either version 3 of the License, or (at
8## your option) any later version.
10## Octave is distributed in the hope that it will be useful, but
11## WITHOUT ANY WARRANTY; without even the implied warranty of
12## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13## General Public License for more details.
15## You should have received a copy of the GNU General Public License
16## along with Octave; see the file COPYING. If not, see
17## <http://www.gnu.org/licenses/>.
20## @deftypefn {Function File} {} factorial (@var{n})
21## Return the factorial of @var{n} where @var{n} is a positive integer. If
22## @var{n} is a scalar, this is equivalent to @code{prod (1:@var{n})}. For
23## vector or matrix arguments, return the factorial of each element in the
24## array. For non-integers see the generalized factorial function
26## @seealso{prod, gamma}
29function x = factorial (n)
32 elseif (any (n(:) < 0 | n(:) != round (n(:))))
33 error ("factorial: n must all be nonnegative integers");
35 x = round (gamma (n+1));
38%!assert (factorial(5), prod(1:5))
39%!assert (factorial([1,2;3,4]), [1,2;6,24])
40%!assert (factorial(70), exp(sum(log(1:70))), -128*eps)
41%!fail ('factorial(5.5)', "must all be nonnegative integers")
42%!fail ('factorial(-3)', "must all be nonnegative integers")
