title: plotting vertical bars instead of points, plot_date
body: <p>I want to plot vertical bars instead of points.  The actual data I have are irregularly spaced, so this will help visualize gaps more easily.
  When I try to plot it, the best I can do are points, which don't increase in size as you zoom in!</p>
  
  <pre><code>import matplotlib
  from matplotlib import pyplot as plt
  import datetime
  
  XX = [datetime.date.today()+datetime.timedelta(x) for x in range(10)]
  YY = range(10)
  plt.plot_date(XX,YY,'o')
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/lYheA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lYheA.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/cGna8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cGna8.png" alt="enter image description here"></a></p>
  
  <p>Any ideas on how I can make taller/bigger (but not wider!) points?</p>