Mercurial > octave
view scripts/linear-algebra/cross.m @ 21308:c53bfd6d8e08
maint: Use American spelling for "behavior".
* Array.cc, randmtzig.c, file-ops.cc, oct-inttypes.h, cross.m, bicgstab.m,
kurtosis.m, skewness.m, build-sparse-tests.sh, __ilu__.cc, __magick_read__.cc:
Use American spelling for "behavior".
author | Rik <rik@octave.org> |
---|---|
date | Fri, 19 Feb 2016 09:40:59 -0800 |
parents | 516bb87ea72e |
children | bac0d6f07a3e |
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## Copyright (C) 1995-2015 Kurt Hornik ## ## 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 3 of the License, 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, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {} {} cross (@var{x}, @var{y}) ## @deftypefnx {} {} cross (@var{x}, @var{y}, @var{dim}) ## Compute the vector cross product of two 3-dimensional vectors @var{x} and ## @var{y}. ## ## If @var{x} and @var{y} are matrices, the cross product is applied along the ## first dimension with three elements. ## ## The optional argument @var{dim} forces the cross product to be calculated ## along the specified dimension. ## ## Example Code: ## ## @example ## @group ## cross ([1,1,0], [0,1,1]) ## @result{} [ 1; -1; 1 ] ## @end group ## @end example ## ## @seealso{dot, curl, divergence} ## @end deftypefn ## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> ## Created: 15 October 1994 ## Adapted-By: jwe function z = cross (x, y, dim) if (nargin != 2 && nargin != 3) print_usage (); endif if (ndims (x) < 3 && ndims (y) < 3 && nargin < 3) ## COMPATIBILITY -- opposite behavior for cross(row,col) ## Swap x and y in the assignments below to get the matlab behavior. ## Better yet, fix the calling code so that it uses conformant vectors. if (columns (x) == 1 && rows (y) == 1) warning ("cross: taking cross product of column by row"); y = y.'; elseif (rows (x) == 1 && columns (y) == 1) warning ("cross: taking cross product of row by column"); x = x.'; endif endif if (nargin == 2) dim = find (size (x) == 3, 1); if (isempty (dim)) error ("cross: must have at least one dimension with 3 elements"); endif else if (size (x, dim) != 3) error ("cross: dimension DIM must have 3 elements"); endif endif nd = ndims (x); sz = size (x); idx2 = idx3 = idx1 = {':'}(ones (1, nd)); idx1(dim) = 1; idx2(dim) = 2; idx3(dim) = 3; if (size_equal (x, y)) x1 = x(idx1{:}); x2 = x(idx2{:}); x3 = x(idx3{:}); y1 = y(idx1{:}); y2 = y(idx2{:}); y3 = y(idx3{:}); z = cat (dim, (x2.*y3 - x3.*y2), (x3.*y1 - x1.*y3), (x1.*y2 - x2.*y1)); else error ("cross: X and Y must have the same dimensions"); endif endfunction %!test %! x = [1 0 0]; %! y = [0 1 0]; %! r = [0 0 1]; %! assert (cross (x, y), r, 2e-8); %!test %! x = [1 2 3]; %! y = [4 5 6]; %! r = [(2*6-3*5) (3*4-1*6) (1*5-2*4)]; %! assert (cross (x, y), r, 2e-8); %!test %! x = [1 0 0; 0 1 0; 0 0 1]; %! y = [0 1 0; 0 0 1; 1 0 0]; %! r = [0 0 1; 1 0 0; 0 1 0]; %! assert (cross (x, y, 2), r, 2e-8); %! assert (cross (x, y, 1), -r, 2e-8); %!error cross (0,0) %!error cross ()