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1 ## Copyright (C) 1998 Auburn University. All rights reserved. |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} qinv (@var{q}) |
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21 ## Return the inverse of a quaternion. |
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22 ## |
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23 ## @example |
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24 ## q = [w, x, y, z] = w*i + x*j + y*k + z |
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25 ## qmult (q, qinv (q)) = 1 = [0 0 0 1] |
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26 ## @end example |
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27 ## @end deftypefn |
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28 |
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29 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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30 ## Adapted-By: jwe |
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31 |
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32 function retval = qinv (q) |
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33 |
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34 if (norm (q) != 0) |
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35 retval = qconj (q) / sum (q .* q); |
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36 else |
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37 error ("qinv: zero quaternion passed!"); |
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38 endif |
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39 |
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40 endfunction |
