title: Subtraction by tracking x y coordinates
body: <p>I have set of arrays:</p>
  
  <pre><code>x1=[1 2 3 4 5 6 7 8 9];
  y1=[1 2 3 4 5 6 7 8 9];
  z1=[2 2 2 2 2 9 6 2 2];
  </code></pre>
  
  <p>and</p>
  
  <pre><code>x2=[6 7];
  y2=[6 7];
  z2=[2 2];
  </code></pre>
  
  <p>by tracking x y coordinates, the z arrays have to be subtracted so that output will be</p>
  
  <pre><code>x=[1 2 3 4 5 6 7 8 9];
  y=[1 2 3 4 5 6 7 8 9];
  z=[2 2 2 2 2 7 4 2 2];
  </code></pre>