How do I find the value for which x% of the array is covered?

Hi all,

I have a 3D array (attached), where I calculated the dose per voxel. Now, I want to find the minimum dose for which 20% of the array is covered (exluding zeros). I've tried the following:

D20_VSV=sort(D_tumorVSV(:),'descend');
result=D20_VSV(1:ceil(length(D20_VSV)*0.9));

This is a simple code (via this question), but doesn't seem to give the wanted result. How should I do this? Thank you in advance!

Answer 1

[Prahlad Gowtham Katte]

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.

1.Non Zeros Function

2.Sort Function

Hope this helps

Thanks