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1 | function d = dot(a, b) |
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2 | % DOT Quaternion dot product. |
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3 | % The dot (scalar) product of two quaternions is the sum of the products of |
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4 | % the (s, x, y, z) components of the two quaternions. |
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5 | |
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6 | % Copyright © 2005 Stephen J. Sangwine and Nicolas Le Bihan. |
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7 | % See the file : Copyright.m for further details. |
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8 | |
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9 | error(nargchk(2, 2, nargin)), error(nargoutchk(0, 1, nargout)) |
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10 | |
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11 | if ~isa(a, 'quaternion') | ~isa(b, 'quaternion') |
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12 | error('Dot product is not defined for a quaternion and a non-quaternion.') |
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13 | end |
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14 | |
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15 | % This function is defined for full and pure quaternions, and combinations |
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16 | % of full and pure, in which case we assume a zero scalar part for the pure |
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17 | % argument. |
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18 | |
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19 | if ispure(a) | ispure(b) |
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20 | % This covers the case where either or both are pure. We can ignore the |
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21 | % scalar part of the other, since it is implicitly multiplied by zero. |
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22 | |
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23 | d = x(a) .* x(b) + y(a) .* y(b) + z(a) .* z(b); |
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24 | else |
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25 | d = s(a) .* s(b) + x(a) .* x(b) + y(a) .* y(b) + z(a) .* z(b); |
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26 | end |
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