How to get XYZ coordinates of all non-zero voxels in a 3D volume?

I have an NxMxP matrix that forms a volume. Programs like ImageJ have a function to save the XY coordinates of any pixels above a certain threshold, is there a good way to implement this in 3D in matlab?

Answer 1

[Ameer Hamza]

Try something like this

M = randi([0 5], 20, 30, 10); % example matrix
idx = find(M); % find nonzero values in M
[y,x,z] = ind2sub(size(M), idx);

y is the row number, x is column number, and z is the 3D slice number of non-zero entries.

[Alexander Collins]

Thanks!

Answer 2

[Rik]

If you want to hide a bit of the implementation that Ameer showed you: I have extended the capabilities of find to more dimensions. You can find my findND function here on the FEX.

M = randi(255, 20, 30, 10); % example matrix
[y,x,z] = findND(M>100);