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2D matrix indexing for element wise operation

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Raj Raj
Raj Raj on 19 Feb 2016
Edited: Star Strider on 19 Feb 2016
Hello all, I am using following code to estimate pairwise angle between for a vector. Where the angle should be between 0 to 2*pi. I am able to predict the angle. But I need your advise on implementing this two for loops. This is slowing the code. Looking forward for your attention. In the code, XYdata is a n x 2 matrix representing the Cartesian coordinates of individual point [xi, yi]. I presume this slow is because of two FOR loops.
for i2 =1:length(XYdata_new)
for j2 = 1:length(XYdata_new)
angle_ij(i2,j2)= Angle360(XYdata_new(i2,1), XYdata_new(i2,2), XYdata_new(j2,1),XYdata_new(j2,2));
Thanks in advance.

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Accepted Answer

Star Strider
Star Strider on 19 Feb 2016
I would use the atan2 or atan2d functions. They are vectorised, so you can likely give your matrix columns to them directly and then do the angle difference calculations.
Star Strider
Star Strider on 19 Feb 2016
My pleasure!
Thank you.
EDIT More efficient versions of the angle conversion lines are:
Angles360 = rem(360+a, 360);
Angles2pi = rem(2*pi+a, 2*pi);

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