Hi
My understanding of the question is that you want to sort a 3-dimensional array and you want to extract the minimum for which 20% of the array is covered excluding zeroes.
The following code snippet can help with the issue
x = C_holllowtumor; %A random 3-dimensional array
y = sort(x(:),'ascend'); % Sorting the array in ascending order
y = nonzero(y); % Extracting the non-zero elements
Result = y(1:ceil(length(y)*0.2)); % Getting the 20% elements
%Result(end) --this would give a single element from the Result.
To know more about sorting and excluding a particular element please refer to the following links.
Hope this helps
Thanks
