MATLAB: Vectorize the code in azimuth calculation.

azimuthlatlongvectorization

Hi I have lots of points(in Latitude & Longitude) and I want to calculate the azimuth of each pairs of them. I use code as attached file 'AzimuthCalc.m'. when I run my function, it's so time consuming and it's elapsed time is 109.371341 seconds. I'm sure the problem caused by my non-vectorize code.
So, would you please check my function and help me to improve it?
Thanks a lot Mani

Best Answer

I don't have the mapping toolbox, so I'm just relying on the documentation to write my answer.
For a start, you can replace the inner loop with:
AzimuthPoints(ii,ii+1:end)=azimuth('rh',lat(ii),long(ii),lat(ii+1:end),long(ii+1:end));
I believe the following may work to replace both loops (and the AzimuthPoints declaration)
[lat1, lat2] = meshgrid(lat);
[long1, long2] = meshgrid(long);
AzimuthPoints = azimuth('rh', lat1, long1, lat2, long2);
The downside of this method is that it's going to calculate the whole AzimuthPoints matrix, not just the upper triangle, so it may actually be slower.
You could do:
lat1 = triu(lat1, 1);
%same with lat2, long1 and long2
to replace the lower triangle and main diagonal with zero, on the assumption that calculating
azimuth('rh', 0, 0, 0, 0)
is faster.
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