title: How to derive equation from Numpy's polyfit?
body: <p>Given an array of x and y values, the following code will calculate a regression curve for these data points.</p>
  
  <pre><code># calculate polynomial
  z = np.polyfit(x, y, 5)
  f = np.poly1d(z)
  
  # calculate new x's and y's
  x_new = np.linspace(x[0], x[-1], 50)
  y_new = f(x_new)
  
  plt.plot(x,y,'o', x_new, y_new)
  plt.xlim([x[0]-1, x[-1] + 1 ])
  plt.show()
  </code></pre>
  
  <p>How can I use the above to derive the actual equation for this curve?</p>