title: How to extract non-overlapping ranges of field 'region' using R?
body: <p>Given a file:</p>
  
  <p>The three columns are: ID, region left and region right.</p>
  
  <pre><code>region1 1 100
  region2 20 120
  region3 101 200
  region4 220 280
  </code></pre>
  
  <p>How could I only extract the regions which are not overlapped?
  To get:</p>
  
  <pre><code>region1 1 100
  region3 101 200
  region4 220 280
  </code></pre>