title: How to make pandas's Series only plot the data in index?
body: <p><strong>EDIT</strong> The missed dates 20140103 and 20140104 is expected, I don't want them to be patched auto.
  And I don't want to use <code>xs = pd.Series(data=range(len(ts)), index=pd.to_datetime(ts))</code> instead of <code>xs = pd.Series(data=range(len(ts)), index=pd.to_datetime(ts))</code> since I want to use some operation as</p>
  
  <pre><code>xs = pd.Series(data=range(len(ts)), index=pd.to_datetime(ts))
  
  xs['2014']
  Out[24]: 
  2014-01-01    0
  2014-01-02    1
  2014-01-05    2
  2014-01-06    3
  2014-01-07    4
  dtype: int64
  </code></pre>
  
  <p>which doesn't work for:</p>
  
  <pre><code>In [26]: xs = pd.Series(data=range(len(ts)), index=ts)
  
  In [27]: xs['2014']
  ---------------------------------------------------------------------------
  KeyError: '2014'
  </code></pre>
  
  <hr>
  
  <p>For example:</p>
  
  <pre><code>In [1]: import pandas as pd
  
  In [2]: ts = ['20140101', '20140102', '20140105', '20140106', '20140107']
  
  In [3]: xs = pd.Series(data=range(len(ts)), index=pd.to_datetime(ts))
  
  In [4]: xs.plot()
  </code></pre>
  
  <p>Will plot this image, which add the extra data on 20140103, 20140104.
  <img src="https://i.stack.imgur.com/vWqg5.png" alt="enter image description here"></p>
  
  <p>While I want to got a image like this:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  
  plt.plot(xs.values)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/tArnv.png" alt="enter image description here"></p>