title: Plot curve using pyplot
body: <p>I have 2 curves with 5 data points:</p>
  
  <pre><code>a = np.array([['16x28', 0.023392, 0.006976],
                ['64x36', 0.029888, 0.039104],
                ['512x288', 0.033328, 2.198592],
                ['1024x576', 0.065632, 5.864992],
                ['3840x2160', 0.801120, 76.550461]])
  </code></pre>
  
  <p>when I plot it, I expect 2 curves but get straight lines instead: </p>
  
  <pre><code>plt.xticks([0,1,2,3, 4],a[:,0])
  plt.plot(a[:,1])
  plt.plot(a[:,2])
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/dIUt9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dIUt9.png" alt="plot curves"></a></p>
  
  <p>How can I make pyplot plot curves like it should be?</p>
  
  <p><strong>UPDATE:</strong> I use Python 3.5.2 and matplotlib 2.1.1</p>