title: How to plot 3 columns in GNUplot?
body: <p>I have files looking like this:</p>
  
  <pre><code>Number Data1 Data2
   1  9.10 4.022
   2  15.27 3.996
   3  21.92 4.004
   4  21.19 4.026
   5  20.67 4.022
   6  20.99 4.000
   7  19.80 4.004
   8  20.01 3.931
   9  20.18 4.004
  10  19.78 4.007
  </code></pre>
  
  <p>I want to plot Number in X axes, Data1 in leftY and Data2 in rightY, but I can not figure out how to do it.</p>
  
  <p>Thanks</p>