extend a Matrix in every iteration
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Hi, I'm having some problems with my code. I have a 3 dimension matrix in which index represent a coordinate, for example, a 10x10x10 array where the first index are 1, 1, 1 represent the point x=1, y=1 and z=1. And the value in the array represent the number of points in theese coordinates. Now I want to use ptCloud function, so I have to extract all the points from my array. What I'm trying is this (If I were in the case 10*10*10 matrix A):
MAT=[]
for i=1:1000
[Yj Xj Zj]=ind2sub(size(A), i);
value=A(Yj Xj Zj);
P=[Yj Xj Zj];
P2=repmat(P,value,1)
MAT=[MAT;P2]
end
With this code I already have a matrix MAT whith every points. But the case is that my array is 200x200x160, and I noticed that in every iteration the time that the code requires increases a lot, so I think there would be something wrong in the for loop.
Thanks so much.
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Accepted Answer
Stephen23
on 18 May 2018
Edited: Stephen23
on 18 May 2018
A = randi(9,10,10,10);
[X,Y,Z] = ind2sub(size(A),1:numel(A));
mat = repelem([X(:),Y(:),Z(:)],A(:),1,1);
but I don't see much point in generating subscript indices: it would be easier to define and use linear indices:
idx = repelem(1:numel(A),A(:).')
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