collapse 3d data set to 2d data set using indexer for 3rd dimension without loops

I have a 3d data set. I want to collapse the 3rd dimension of this data set. I have a 2d data set which represents the points i want to keep in the collapsing of the 3d data set. How can I accomplish this without having to use loops? This is how I am doing it now (with loops):

data = rand(100,100,10);
[xx,yy] = meshgrid(1:100,1:100);
zz = round(.03*xx+.05*yy);
zz(zz<1) = 1;

for i = 1:size(data,1)
    for j = 1:size(data,2)
        collapsedData(i,j) = data(i,j,zz(i,j));
    end
end

[Star Strider]

It’s difficult to understand what you are doing because we have no idea what ‘zz’ is or how it relates to ‘data’. If would help if you gave numeric example of ‘data’ and what you want ‘collapsedData’ to be.

[Stephen23]

Note that you should not use i or j for the loop variables, as these are both names of the inbuilt imaginary unit .

Answer 1

[David Young]

[yy, xx] = ndgrid(1:size(data,1), 1:size(data,2));
collapsedData = data(sub2ind(size(data), yy, xx, zz))

[Victor]

Perfect. Thanks, David.