title: Value error x and y must be same size, but they are?
body: <p>I'm trying to plot to numpy arrays both of length 10 against one another:</p>
  
  <pre><code>mass_frac_plot = plt.figure()
  mass_frac = mass_frac_plot.add_subplot(1, 1, 1)
  mass_frac.scatter(mass_frac, homogen_frac)
  </code></pre>
  
  <p>I get this:</p>
  
  <pre><code>Traceback (most recent call last):
    File "./plot.py", line 58, in &lt;module&gt;
      mass_frac.scatter(mass_frac, homogen_frac)
    File "/usr/local/lib/python3.5/site-packages/matplotlib/__init__.py", line 1811, in inner
      return func(ax, *args, **kwargs)
    File "/usr/local/lib/python3.5/site-packages/matplotlib/axes/_axes.py", line 3836, in scatter
      raise ValueError("x and y must be the same size")
  </code></pre>
  
  <p>Help! They really are both arrays and of length 10...</p>
  
  <pre><code>print(type(mass_frac), len(mass_frac))
  print(mass_frac)
  print(type(homogen_frac), len(homogen_frac))
  print(homogen_frac)
  </code></pre>
  
  <p>Gives this: </p>
  
  <pre><code>&lt;class 'numpy.ndarray'&gt; 10
  [ 3.67  3.6   4.45  3.74  4.93  4.35  3.89  5.62  4.73  3.83]
  &lt;class 'numpy.ndarray'&gt; 10
  [  98.02982123   96.82921968   88.8207858    83.37174016   75.55236146
  87.71156752   91.95410515   66.34245085   77.63112123  119.74640558]
  </code></pre>