title: Plotly boxplot: groupby option?
body: <p>I have two boolean variables and I try to create a boxplot with groups. Each group should represent one of the variables and it should contain two boxplots, one for TRUE and one for FALSE. Instead I am getting two groups, one representing TRUE and one representing FALSE and for each group two boxplots corresponding to each variable as in the attached graph:</p>
  
  <p><img src="https://i.stack.imgur.com/iu0ex.png" alt="boxplot"></p>
  
  <p>I understand that groups are derived from the xaxis. But how can I make plotly think that the variable names are the groups? The code I used for the output :</p>
  
  <pre><code>trace3= Box(
   y=raw_matrix.TPS,
   x=raw_matrix.noClassGc,
   name='noClassGc',
   marker=Marker(
   color='#3F5D7D'
  ))
  
  trace4= Box(
   y=raw_matrix.TPS,
   x=raw_matrix.aggresiveOpts,
   name='aggresiveOpts',
   marker=Marker(
   color='#0099FF'
   ))
  
  data = Data([trace3, trace4])
  layout = Layout(
   yaxis=YAxis(
   title='confidence',
   zeroline=False),
   boxmode='group',
   boxgroupgap=0.5
   )
  
  
  fig = Figure(data=data, layout=layout)
  plot_url = ploteczki.plot(fig, filename='Performance by categoricals parameters')
  </code></pre>