title: Pandas ValueError: too many values to unpack np.polyfit
body: <p>I am trying to do a polynomial regression on some data I have. I have been able to successfully call </p>
  
  <p><code>m, b = np.polyfit(x.values.flatten(), y.values.flatten(), 1)</code></p>
  
  <p>However when I increase the degree to anything higher than 1, then I get the following error: </p>
  
  <pre><code>np.polyfit(x.values.flatten(), y.values.flatten(), 2)
  ValueError: too many values to unpack
  </code></pre>
  
  <p>I am reading data as:</p>
  
  <pre><code>x = pandas.read_csv('D3.csv', usecols = [0])
  y = pandas.read_csv('D3.csv', usecols = [3])
  </code></pre>
  
  <p>Any idea why this might be happening?</p>