title: Var(x) and cov(x, x) don't give the same result in numpy
body: <p>A property of the covariance is, that cov(x, x) = var(x)</p>
  
  <p>However, in numpy I don't get the same result.</p>
  
  <pre><code>from numpy import var, cov
  
  x = range(10)
  y = var(x)
  z = cov(x, x)[0][1]
  print y, z
  </code></pre>
  
  <p>Am I doing something wrong here? How can I obtain the correct result?</p>