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.
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Accepted Answer
Jan
on 13 Jun 2013
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 Comments
Stephen Devlin
on 16 Mar 2018
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
on 3 Dec 2018
@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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