title: gnuplot: draw polygon from data
body: <p>How can I plot polygons with data coming from a file? For example if I have a file containing coordinates of the edges of a four-point polygon for each data point, how would I proceed?</p>
  
  <p>e.g. a data file containing</p>
  
  <pre><code>0 0 0 1 1 1 1 0
  2 2 2 3 3 3 3 2
  </code></pre>
  
  <p>should draw two quadratic rectangular wit center at position (0.5,0.5) and (2.5,2.5).</p>