title: what is the best way to remove a row or col from a cv mat
body: <p>Assume that I have a mat object such as follow:</p>
  
  <pre><code>mat = 
     [75, 97, 66, 95, 15, 22;
      24, 21, 71, 72, 34, 66;
      21, 69, 88, 72, 64, 1;
      26, 47, 26, 40, 95, 24;
      70, 37, 9, 83, 16, 83];
  </code></pre>
  
  <p>and I want to remove a row from it say second row to have a mat like this:</p>
  
  <pre><code> [75, 97, 66, 95, 15, 22;
   21, 69, 88, 72, 64, 1;
   26, 47, 26, 40, 95, 24;
   70, 37, 9, 83, 16, 83]
  </code></pre>
  
  <p>or deleting a col say col 3:</p>
  
  <pre><code>[75, 97,  95, 15, 22;
   24, 21,  72, 34, 66;
   21, 69,  72, 64, 1;
   26, 47,  40, 95, 24;
   70, 37,  83, 16, 83]
  </code></pre>
  
  <p>what is the fastest way to do this? I can break the matrix into to ROI and then merge them to each other, but is there any better way?</p>