Mercurial > hg > octave-lyh
annotate scripts/linear-algebra/cross.m @ 9245:16f53d29049f
update copyright notices
| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Fri, 22 May 2009 10:46:00 -0400 |
| parents | 8c71a86c4bf4 |
| children | cac3b4e5035b |
| rev | line source |
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| 7017 | 1 ## Copyright (C) 1995, 1996, 1997, 1999, 2000, 2002, 2004, 2005, 2006, |
| 9245 | 2 ## 2007, 2009 Kurt Hornik |
| 3426 | 3 ## |
| 3922 | 4 ## This file is part of Octave. |
| 5 ## | |
| 6 ## Octave is free software; you can redistribute it and/or modify it | |
| 7 ## under the terms of the GNU General Public License as published by | |
| 7016 | 8 ## the Free Software Foundation; either version 3 of the License, or (at |
| 9 ## your option) any later version. | |
| 3426 | 10 ## |
| 3922 | 11 ## Octave is distributed in the hope that it will be useful, but |
| 2540 | 12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 14 ## General Public License for more details. |
| 15 ## | |
| 2540 | 16 ## You should have received a copy of the GNU General Public License |
| 7016 | 17 ## along with Octave; see the file COPYING. If not, see |
| 18 ## <http://www.gnu.org/licenses/>. | |
| 2540 | 19 |
| 3321 | 20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} cross (@var{x}, @var{y}) |
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8c71a86c4bf4
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parents:
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22 ## @deftypefnx {Function File} {} cross (@var{x}, @var{y}, @var{dim}) |
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8c71a86c4bf4
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Rik <rdrider0-list@yahoo.com>
parents:
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23 ## Compute the vector cross product of two 3-dimensional vectors |
| 3418 | 24 ## @var{x} and @var{y}. |
| 25 ## | |
| 3321 | 26 ## @example |
| 27 ## @group | |
| 28 ## cross ([1,1,0], [0,1,1]) | |
| 29 ## @result{} [ 1; -1; 1 ] | |
| 30 ## @end group | |
| 31 ## @end example | |
| 3883 | 32 ## |
| 4890 | 33 ## If @var{x} and @var{y} are matrices, the cross product is applied |
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34 ## along the first dimension with 3 elements. The optional argument |
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parents:
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35 ## @var{dim} forces the cross product to be calculated along |
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8c71a86c4bf4
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Rik <rdrider0-list@yahoo.com>
parents:
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36 ## the specified dimension. |
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8c71a86c4bf4
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37 ## @seealso{dot} |
| 3321 | 38 ## @end deftypefn |
| 2540 | 39 |
| 5428 | 40 ## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> |
| 2540 | 41 ## Created: 15 October 1994 |
| 42 ## Adapted-By: jwe | |
| 43 | |
| 4890 | 44 function z = cross (x, y, dim) |
| 3883 | 45 |
| 4890 | 46 if (nargin != 2 && nargin != 3) |
| 6046 | 47 print_usage (); |
| 4890 | 48 endif |
| 49 | |
| 50 if (ndims (x) < 3 && ndims (y) < 3 && nargin < 3) | |
| 5775 | 51 ## COMPATIBILITY -- opposite behaviour for cross(row,col) |
| 4890 | 52 ## Swap x and y in the assignments below to get the matlab behaviour. |
| 53 ## Better yet, fix the calling code so that it uses conformant vectors. | |
| 54 if (columns (x) == 1 && rows (y) == 1) | |
| 55 warning ("cross: taking cross product of column by row"); | |
| 56 y = y.'; | |
| 57 elseif (rows (x) == 1 && columns (y) == 1) | |
| 58 warning ("cross: taking cross product of row by column"); | |
| 59 x = x.'; | |
| 60 endif | |
| 2540 | 61 endif |
| 62 | |
| 4890 | 63 if (nargin == 2) |
| 6024 | 64 dim = find (size (x) == 3, 1); |
| 4890 | 65 if (isempty (dim)) |
| 66 error ("cross: must have at least one dimension with 3 elements"); | |
| 67 endif | |
| 68 else | |
| 69 if (size (x) != 3) | |
| 70 error ("cross: dimension dim must have 3 elements"); | |
| 71 endif | |
| 3883 | 72 endif |
| 3085 | 73 |
| 4890 | 74 nd = ndims (x); |
| 75 sz = size (x); | |
| 5108 | 76 idx1 = cell (1, nd); |
| 4890 | 77 for i = 1:nd |
| 78 idx1{i} = 1:sz(i); | |
| 79 endfor | |
| 80 idx2 = idx3 = idx1; | |
| 81 idx1(dim) = 1; | |
| 82 idx2(dim) = 2; | |
| 83 idx3(dim) = 3; | |
| 84 | |
| 6157 | 85 if (size_equal (x, y)) |
| 4890 | 86 z = cat (dim, |
| 87 (x(idx2{:}) .* y(idx3{:}) - x(idx3{:}) .* y(idx2{:})), | |
| 88 (x(idx3{:}) .* y(idx1{:}) - x(idx1{:}) .* y(idx3{:})), | |
| 89 (x(idx1{:}) .* y(idx2{:}) - x(idx2{:}) .* y(idx1{:}))); | |
| 3085 | 90 else |
| 3883 | 91 error ("cross: x and y must have the same dimensions"); |
| 2540 | 92 endif |
| 93 | |
| 94 endfunction |