title: Sorting data by multiple columns
body: <p>I have a question about sorting data by multiple columns. I'm definitely a beginner at this and am wondering how I can sort by one column and then by another without losing the ordering of the first column. I have a file of tab separated data consisting of three columns. The majority of the data isn't paired (one id, first column, and position start and end, second and third columns). Occasionally, however, there are multiple entries for the same ID (first column). These need to remain grouped together (without a space separating them from the next entry, unless it has a different ID). The data is really already sorted with respect to the first column, but I need to sort it numerically based on the starting position (second column) while preserving the original sorting. Like this:</p>
  
  <p>Current format:</p>
  
  <pre><code>PITG_00129  606 1436
  
  PITG_00130  1   987
  
  PITG_00132  2   1321
  
  PITG_00133 4464 11708
  PITG_00133 1 2946
  PITG_00133 4081 4515
  </code></pre>
  
  <p>Desired format:</p>
  
  <pre><code>PITG_00129  606 1436
  
  PITG_00130  1   987
  
  PITG_00132  2   1321
  
  PITG_00133 1 2946
  PITG_00133 4081 4515
  PITG_00133 4464 11708
  </code></pre>