title: How to make a plot in plotly using pandas - value_counts() as one choice in axis
body: <p>I would like to plot a bar chart in plotly with x-axis being days of the week and y-axis being the count of emails received per weekday. </p>
  
  <p>I have the data in pandas dataframe in this manner: </p>
  
  <pre><code>    df_res.Weekday.value_counts()
  
  
      Tuesday      331
      Monday       292
      Wednesday    282
      Friday       258
      Thursday     203
      Saturday       4
      Name: Weekday, dtype: int64
  
      CODE to plot the bar chart
      x = df_pete['Weekday']
      y = df_res[df_res['Volunteer'] == 'pete'].groupby('Volunteer').Weekday.value_counts()
  
      df = pd.DataFrame({'x': x, 'y': y})
      df.head()
  
      data = [
            go.Bar(
                x=df['x'],
                y=df['y'])
             ]
  
      layout=go.Layout(title="Emails per weekday", xaxis={'title':'Weekday'}, yaxis={'title':'Email count'})
      fig = go.Figure(data=data, layout=layout)
      py.iplot(fig)
  </code></pre>
  
  <p>Error message: KeyError: 'Weekday'</p>
  
  <p>PS - I hope the code is indented properly, apologies for any code that isn't. </p>