text: #######################################################################
  #
  # An example of creating an Excel Line chart with a secondary axis
  # using Python and XlsxWriter.
  #
  # Copyright 2013-2021, John McNamara, jmcnamara@cpan.org
  #
  import xlsxwriter
  
  workbook = xlsxwriter.Workbook('chart_secondary_axis.xlsx')
  worksheet = workbook.add_worksheet()
  bold = workbook.add_format({'bold': 1})
  
  # Add the worksheet data that the charts will refer to.
  headings = ['Aliens', 'Humans']
  data = [
      [2, 3, 4, 5, 6, 7],
      [10, 40, 50, 20, 10, 50],
  ]
  
  worksheet.write_row('A1', headings, bold)
  worksheet.write_column('A2', data[0])
  worksheet.write_column('B2', data[1])
  
  
  # Create a new chart object. In this case an embedded chart.
  chart = workbook.add_chart({'type': 'line'})
  
  # Configure a series with a secondary axis
  chart.add_series({
      'name':   '=Sheet1!$A$1',
      'values': '=Sheet1!$A$2:$A$7',
      'y2_axis': 1,
  })
  
  chart.add_series({
      'name':   '=Sheet1!$B$1',
      'values': '=Sheet1!$B$2:$B$7',
  })
  
  chart.set_legend({'position': 'right'})
  
  # Add a chart title and some axis labels.
  chart.set_title({'name': 'Survey results'})
  chart.set_x_axis({'name': 'Days', })
  chart.set_y_axis({'name': 'Population', 'major_gridlines': {'visible': 0}})
  chart.set_y2_axis({'name': 'Laser wounds'})
  
  # Insert the chart into the worksheet (with an offset).
  worksheet.insert_chart('D2', chart, {'x_offset': 25, 'y_offset': 10})
  
  workbook.close()
  