Efficient calculation of 3d matrix of distances
1 次查看(过去 30 天)
显示 更早的评论
Dear;
I would like to calculate the 3D matrix of distances between one point an each element of a 3D matrix in an efficient way.
Without vectorization the code is:
MDistances=zeros(size(M));
for i=1:size(M,1)
for j=1:size(M,2)
for k=1:size(M,3)
MDistances(i,j,k)=(i-ip)^2+(j-jp)^2+(k-kp)^2
end
end
end
MDistances=sqrt(MDistances);
Thanks a lot!!
0 个评论
采纳的回答
Adam
2016-8-3
[x, y, z] = meshgrid( (j-jp)^2, (i-ip)^2, (k-kp)^2 );
distSq = x + y + z;
MDistances = sqrt( distSq );
should give the correct answer I think. I always get confused with meshgrid though how my x and y inputs and outputs always seem to be the wrong way round. When I did the obvious approach I ended up with an answer that didn't match expectations so swapping i and j around in the inputs seems to give the right answer.
Maybe someone else can expand on why that is the case as I don't have the time to re-remember!
2 个评论
Adam
2016-8-3
Ah yes, I forgot to include that I had created those in the same way you do for each of your loops.
更多回答(0 个)
另请参阅
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!