title: linear interpolation between two data points
body: <p>I have two data points <code>x</code> and <code>y</code>:</p>
  
  <pre><code>  x = 5 (value corresponding to 95%)
    y = 17 (value corresponding to 102.5%)
  </code></pre>
  
  <p>No I would like to calculate the value for <code>xi</code> which should correspond to 100%. </p>
  
  <pre><code> x = 5 (value corresponding to 95%)
   xi = ?? (value corresponding to 100%)
   y = 17 (value corresponding to 102.5%)
  </code></pre>
  
  <p>How should I do this using python?</p>