title: Converting well number to the identifier on a 96 well plate
body: <p>In a 96 well plate there are 8 columns (A,B,...) and 12 rows (01 ... 12);
  so the plate looks like this:</p>
  
  <pre><code>A01 A02 ... A12
  B01 B02 ... B12
  C01 ...
  ...
  H01 ..
  </code></pre>
  
  <p>Currently I have identified the plates as:</p>
  
  <pre><code> 1 2 3 4 ... 12
   13 14 15 ...24
   ..
   84 ...      96
  </code></pre>
  
  <p>How can I write a function <code>wellnumber2wellidentifier</code> to convert the numerical index into the format used on the top? For example, well <code>1</code> would return <code>A01</code> and well <code>13</code> would return <code>B01</code>.</p>