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40 lines
1.4 KiB
40 lines
1.4 KiB
%VEX Convert skew-symmetric matrix to vector
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%
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% V = VEX(S) is the vector (3x1) which has the skew-symmetric matrix S (3x3)
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%
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% | 0 -vz vy|
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% | vz 0 -vx|
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% |-vy vx 0 |
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%
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% Notes::
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% - This is the inverse of the function SKEW().
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% - No checking is done to ensure that the matrix is actually skew-symmetric.
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% - The function takes the mean of the two elements that correspond to each unique
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% element of the matrix, ie. vx = 0.5*(S(3,2)-S(2,3))
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%
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% See also SKEW.
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% Copyright (C) 1993-2011, by Peter I. Corke
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%
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% This file is part of The Robotics Toolbox for Matlab (RTB).
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%
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% RTB is free software: you can redistribute it and/or modify
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% it under the terms of the GNU Lesser General Public License as published by
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% the Free Software Foundation, either version 3 of the License, or
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% (at your option) any later version.
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%
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% RTB is distributed in the hope that it will be useful,
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% but WITHOUT ANY WARRANTY; without even the implied warranty of
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% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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% GNU Lesser General Public License for more details.
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%
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% You should have received a copy of the GNU Leser General Public License
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% along with RTB. If not, see <http://www.gnu.org/licenses/>.
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function v = vex(S)
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if isrot(S) || ishomog(S)
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v = 0.5*[S(3,2)-S(2,3); S(1,3)-S(3,1); S(2,1)-S(1,2)];
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else
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error('argument must be a 3x3 matrix');
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end
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