title: Holt winters initial Seasonal Indices calculation in python
body: <p>I am having trouble finding the correct calculations for the seasonal indicies for the Holt Winters exponential smoothing.</p>
  
  <p>I used the calculation method from <a href="http://www.itl.nist.gov/div898/handbook/pmc/section4/pmc435.htm" rel="nofollow noreferrer">NIST</a> and used data from <a href="http://adorio-research.org/wordpress/?p=1230" rel="nofollow noreferrer">adorio-research</a></p>
  
  <pre><code>z =[146, 96, 59, 133, 192, 127, 79, 186, 272, 155, 98, 219]
  
  
  Results:
  s= [ 1.3744  0.8627  0.5373  1.2257]
  </code></pre>
  
  <p>The calculations using the NIST method is <a href="https://stackoverflow.com/questions/20872202/efficiently-iterating-with-numpy">here</a> on Stackoverflow. But for <a href="http://adorio-research.org/wordpress/?p=1230" rel="nofollow noreferrer">adorio-research</a> they got different results with the same values.</p>
  
  <pre><code>Results:
  S= [ 1.4789  0.8985  0.5152  1.1074]
  </code></pre>
  
  <p>Did I calculate something wrong or is the code for adorio-research using a different method to calculate the initial seasonal indices?</p>