title: Sorting a 2 dimensional array
body: <p>I've got a 2D array that I'd like to sort into descending order depending on the contents of the first column, however I'd like the array to retain each row and move the second column as the first moves. To put it into an example;</p>
  
  <pre><code>[2, 5]
  [4, 18]
  [1, 7]
  [9, 3]
  </code></pre>
  
  <p>would be sorted into:</p>
  
  <pre><code>[9, 3]
  [4, 18]
  [2, 5]
  [1, 7]
  </code></pre>
  
  <p>Thanks.</p>