title: Pandas plot bar: legends of other columns appears in plot
body: <p>I have the following code and run it on jupyter. </p>
  
  <pre><code># Make the 4 plots:
  import matplotlib.pyplot as plt
  # Dwell Time
  ax = hour_17['Average Dwell Time'].plot(kind='bar', figsize=(15, 10), 
  legend=True, fontsize=12)
  ax.set_xlabel("5-minutes interval between 17:00-18:00", fontsize=12)
  ax.set_ylabel("Time (sec)", fontsize=12)
  plt.savefig('name1.jpeg')
  
  # Waiting Time
  ax = hour_17['Average Waiting Time'].plot(kind='bar', figsize=(15, 10), 
  legend=True, fontsize=12)
  ax.set_xlabel("5-minutes interval between 17:00-18:00", fontsize=12)
  ax.set_ylabel("Time (sec)", fontsize=12)
  plt.savefig('name2.jpeg')
  </code></pre>
  
  <p>There the following problems regarding it:
  The first plot displays the indicated column and legend, while the second plot contains two legend: Average Waiting time and Average Dwell Time and displays the same information as the first plot.
  In reality I have to plot data from 4 columns, so the last plot contains 4 legends. </p>
  
  <p>Any idea of what is going on? Thank you!</p>