--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/general/trapz.m	Wed May 17 21:00:54 2006 +0000
@@ -0,0 +1,106 @@
+## Copyright (C) 2000  Kai Habel
+##
+## 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.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{z} =} trapz (@var{y})
+## @deftypefnx {Function File} {@var{z} =} trapz (@var{x}, @var{y})
+## @deftypefnx {Function File} {@var{z} =} trapz (@dots{}, @var{dim})
+## 
+## Numerical intergration using trapezodial method. @code{trapz
+## (@var{y})} computes the integral of the @var{y} along the first
+## non singleton dimension. If the argument @var{x} is omitted a 
+## equally spaced vector is assumed. @code{trapz (@var{x}, @var{y})} 
+## evaluates the integral with respect to @var{x}.
+##  
+## @seealso{cumtrapz}
+## @end deftypefn
+
+## Author:	Kai Habel <kai.habel@gmx.de>
+##
+## also: June 2000 - Paul Kienzle (fixes,suggestions) 
+## 2006-05-12 David Bateman - Modified for NDArrays
+
+function z = trapz (x, y, dim)
+	
+
+  if (nargin < 1) || (nargin > 3)
+    usage ("trapz (x, y, dim)");
+  endif
+
+  nd = ndims (x);
+  sz = size (x);
+
+  have_x = false;
+  have_dim = false;
+  if (nargin == 3)
+    have_x = true;
+    have_dim = true;
+  endif
+  if (nargin == 2)
+    if (size (x) != size (y) && isscalar (y))
+      dim = y;
+      have_dim = true;
+    else
+      have_x = true;
+    endif
+  endif
+
+  if (! have_dim)
+    ## Find the first singleton dimension.
+    dim = 0;
+    while (dim < nd && sz(dim+1) == 1)
+      dim++;
+    endwhile
+    dim++;
+    if (dim > nd)
+      dim = 1;
+    endif
+  else
+    dim = floor (dim);
+    if (dim < 1 || dim > nd)
+      error ("cumtrapz: invalid dimension along which to sort");
+    endif
+  endif
+ 
+  n = sz(dim);
+  idx1 = cell ();
+  for i = 1:nd
+    idx1{i} = 1:sz(i);
+  endfor
+  idx2 = idx1;
+  idx1{dim} = 2 : n;	
+  idx2{dim} = 1 : (n - 1);
+
+  if (! have_x)
+    z = 0.5 * sum (x(idx1{:}) + x(idx2{:}), dim);
+  else
+    if (size (x) != size (y))
+      error ("cumtrapz: x and y must have same shape");
+    endif
+    z = 0.5 * sum ((x(idx1{:}) - x(idx2{:})) .* 
+		   (y(idx1{:}) + y(idx2{:})), dim);
+  endif
+endfunction
+
+%!assert (trapz(1:5), 12)
+%!assert (trapz(0:0.5:2,1:5), 6)
+%!assert (trapz([1:5;1:5],2),[12;12])
+%!assert (trapz([1:5;1:5].',1),[12,12])
+%!assert (trapz([0:0.5:2;0:0.5:2],[1:5;1:5],2),[6;6])
+%!assert (trapz([0:0.5:2;0:0.5:2].',[1:5;1:5].',1),[6,6])