title: Line on a python graph doesn't connect each point chronologically
body: <p>I've made a graph that plots the change in the price of a ticket with the dates being on the x-axis and the ticket price being on the y-axis. For some reason, the line that connects the point starts at the first point, goes to the last point and then looks like it connects back to the other two points instead of connecting chronologically by date. This seems like a simple issue to fix, but I can't tell what I'm doing wrong from looking at my code as I'm still very new to using matplotlib. Here is the snippet of code that makes the graph:</p>
  
  <pre><code>fig, ax = plt.subplots()
  ax.xaxis_date()
  # Set date format and major locator of x-axis
  plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%m'+ '/' '%d' + '/' '%Y'))
  plt.gca().yaxis.set_major_locator(mdates.DayLocator())
  graph = fig.add_subplot(111)
  xs = [x[0] for x in rows]
  ys = [y[1] for y in rows]
  
  plt.plot(xs,ys, 'r-o')
  plt.gcf().autofmt_xdate()
  graph.set_xticks(xs)
  plt.title("Ticket Prices over the course of a month")
  plt.xlabel("Date")
  plt.ylabel("Ticket Price")  
  </code></pre>
  
  <p>Based on the code, what could be causing the problem? An image of the graph is below:</p>
  
  <p><a href="https://i.stack.imgur.com/xQTvr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xQTvr.png" alt="enter image description here"></a></p>