--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/general/nthroot.m	Mon May 22 06:25:14 2006 +0000
@@ -0,0 +1,71 @@
+## Copyright (C) 2004 Paul Kienzle
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2, or (at your option)
+## any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301, USA.
+##
+## Original version by Paul Kienzle distributed as free software in the
+## public domain.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} nthroot (@var{x}, @var{n})
+## 
+## Compute the nth root of @var{x}, returning real results for real 
+## components of @var{x}. For example
+##
+## @example
+## @group
+## nthroot (-1, 3)
+## @result{} -1
+## (-1) ^ (1 / 3)
+## @result{} 0.50000 - 0.86603i
+## @end group
+## @end example
+##
+## @end deftypefn
+
+function y = nthroot (x, m)
+
+  if (nargin != 2)
+    print_usage ();
+  endif
+  
+  y = x.^(1./m);
+
+  if (isscalar (x))
+    x *= ones (size (m)); 
+  endif
+
+  if (isscalar (m))
+    m *= ones (size (x)); 
+  endif
+
+  idx = (mod (m, 2) == 1 & imag (x) == 0 & x < 0);
+
+  if (any (idx(:)))
+    y(idx) = -(-x(idx)).^(1./m(idx)); 
+  endif
+
+  ## If result is all real, make sure it looks real
+  if (all (imag (y) == 0))
+    y = real (y); 
+  endif
+
+endfunction
+
+%!assert(nthroot(-1,[3,-3]), [-1,-1],eps);
+%!assert(nthroot([-1,1],[3.1,-3]), [-1,1].^(1./[3.1,-3]));
+%!assert(nthroot([-1+1i,-1-1i],3), [-1+1i,-1-1i].^(1/3));