Logical indexing in multidimensional array

I have a 4-dimensional array and would like to replace parts of it with NaN values. The array has dimensions 60 x 321 x 28 x 16, the first three dimensions are some parameters I iterated through, the last dimension is the actual results I obtained. I would now like to replace some of the results, depending on the value of one of the elements from the results. I tried this:

res = % some 4D array (60 x 231 x 28 x 16)

res(res(:,:,:,9) > 5, 4:16) = NaN;      % Fail

What I want to obtain would be something like this:

for x=1:60
    for y=1:321
        for z=1:28
            if res(x,y,z,9) > 5
                res(x,y,z,4:16) = NaN;
            end
        end
    end
end

Is there a more compact way of writing this?

[Jan]

This is a good question. To my surprise I did not even find a built-in function for this. I'd expect a function for masking [M x N x 3] arrays (RGB-images) in the image processing toolbox.

Answer 1

[Matt J]

T=reshape(res,[],16);
T(T(:,9)>5,4:16)=nan;

res=reshape(T,size(res));