title: Fill area under curve in matlibplot python on log scale
body: <p>I'm trying to fill the area under a curve with matplotlib. The script below works fine. </p>
  
  <pre><code>import matplotlib.pyplot as plt
  from math import sqrt
  x = range(100)
  y = [sqrt(i) for i in x]
  plt.plot(x,y,color='k',lw=2)
  plt.fill_between(x,y,0,color='0.8')
  plt.show()
  </code></pre>
  
  <p>However if I set the y-scale to logarithmic (see below). It sometimes fills the area above the curve ! Can anyone help me? I would like to fill the area between the curve and y = 0.</p>
  
  <pre><code>x = range(100)
  y = [sqrt(i) for i in x]
  plt.plot(x,y,color='k',lw=2)
  plt.fill_between(x,y,0,color='0.8')
  plt.yscale('log')
  plt.show()
  </code></pre>
  
  <p>Thanks in advance!</p>