title: Find the elements in an array that is not in another array
body: <p>I have two arrays lets say A = [1;2;4;7;10;20];
  B = [1;4;8];</p>
  
  <p>Now I want to find the elements of A, that are not in B i.e; [2;7;10;20]. I just need their index that is the index of the elements [2;7;10;20] in A. How can I implement this in matlab. I can use loops and all. But that is not what I want. I want an elegant solution. Suggestions?</p>