How to Vectorize this Code?
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I have this 147000 x 3 array, where each index represents a 3D vector. I want to use the vector at each index to find the angle between it and a predefined vector "b0" [ 0 1 0], this results in a 147000 x 1 array where each index has a single angle. I have been able to do this by using a normal for loop, however I was wondering if there was a way to vectorize this so it will be faster. I have been trying, but it either says that it can't do the dot product because arrays are of incompatible size, or it will only calculate the angle of the first index, then copy that 147000 times into the Nx1 array.
Thanks for any help. ![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1132235/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1132235/image.png)
4 Comments
Matt J
on 21 Sep 2022
@Krishan Bansal Please post your code and output as text, not images, to facilitate copy/pasting.
Accepted Answer
Matt J
on 21 Sep 2022
Edited: Matt J
on 21 Sep 2022
n3Array=normalize(n3Array,2,'n');
b0=b0/norm(b0);
b0angles=acosd(n3Array*b0);
11 Comments
James Tursa
on 21 Sep 2022
This creates complex doubles?
n3Array = squeeze(Orientation4D(:, 1, 1,1:3));
b0 = [0 1 0];
n3Array = normalize(n3Array,2,'n');
b0 = b0/norm(b0);
b0angles = acosd(n3Array*b0(:));
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