Calculate the angle between multiple points
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I have a matrix A contain x values in the first column and y values in the second column. I want to calculate the angle between vectors.
1 个评论
Jan
2013-6-13
There is no "angle between points". Do you mean the angle between two vectors?
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Jan
2013-6-13
The ACOS and the corresponding ASIN approchs are numerically instable near to multiples of pi (half). Better use the more accurate ATAN2 method:
angle = atan2(norm(cross(v1,v2)), dot(v1,v2));
4 个评论
Roger Stafford
2013-6-17
编辑：Roger Stafford
2013-6-17
In the two-dimensional x-y plane Mathworks' 'cross' function doesn't work. It requires three-element vectors. The two-dimensional expression should be:
angle = atan2(abs(det([v1;v2])),dot(v1,v2));
where v1 and v2 are assumed to be two-element row vectors.
(Corrected)
Jan
2013-6-18
@Roger: Thanks! I forgot the limitations of cross.
Stephen Devlin
2018-3-16
Hi, I have no idea if anyone will see this comment as it is years after the original post, but mathematically what is this expression:
"angle = atan2(abs(det([v1;v2])),dot(v1,v2));"
Jess Smith
2018-12-3
@stephen thats basically doing the inverse tangent of the cross product of 2D vectors over the dot product of those vectors, giving you the angle; cross product of a x b is |a||b|sin(theta) and dot product is |a||b|cos(theta) so dividing them by each other and taking inverse tan is the angle
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michael scheinfeild
2014-7-9
0 个投票
what is v1 v2 can yo give example
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