title: Charts multi type and secondary Y axis
body: <p>I'm creating a chart which had 3 series, 2 which are columns, and I need a line which runs through which shows the average.</p>
  
  <p>I have found trendlines but at the moment my chart is showing a series column and a trendline when I just want to see the trend line. Here is the code:</p>
  
  <pre><code>// Add a chart for the country. i.e. show the 
  var chart = worksheet.Drawings.AddChart(countryName + "Click through report", eChartType.ColumnClustered);
  
  // Set the size of the chart
  chart.SetSize(1150, 540);
  
  //Set the series value for each column - impressions
  int chartrange = cumCtrj + 27;
  var series1 = chart.Series.Add("=" + countryName + "!$B$29:$B$" + chartrange, "=" + countryName + "!$A$29:$A$" + chartrange);
  series1.Header = "Dealer Lists Displayed";
  
  // column - Clicks
  var series2 = chart.Series.Add("=" + countryName + "!$C$29:$C$" + chartrange, "=" + countryName + "!$A$29:$A$" + chartrange);
  series2.Header = "Clicks To Dealer";
  
  var series3 = chart.Series.Add("=" + countryName + "!$D$29:$D$" + chartrange, "=" + countryName + "!$A$29:$A$" + chartrange);
  series3.Header = "Click Through Rate";
  series3.TrendLines.Add(eTrendLine.Linear);
  </code></pre>
  
  <p>How can I just have the trendline without the column?</p>
  
  <p>EDIT:  I'm not actually certain that it is trendlines that i need - as the values are actually in the table (- the CTR rate is the clicks/impressions* 100 and is a percentage value) - but i need this shown as a line going through the other two columns.</p>
  
  <p>Below is an example of the table that i am working from.</p>
  
  <pre><code>Row Impressions Clicks CTR
  
  40  391 4   1.0210593
  41  986 35  3.5491558
  42  104 37  3.534818
  43  236 38  16.064257
  44  579 10  1.72592337
  </code></pre>
  
  <p>EDIT 2:
  I have found the way to add a line (so a second chart type to my chart please see the following code:</p>
  
  <pre><code>   // TODO click through rate as a line.
                              var chartType2 = chart.PlotArea.ChartTypes.Add(eChartType.Line);
                              var series3 = chartType2.Series.Add("=" + countryName + "!$D$29:$D$" + chartrange, "=" + countryName + "!$A$29:$A$" + chartrange);
                              series3.Header = "Click Through Rate";
  </code></pre>
  
  <p><strong>The final thing that i need to do</strong> is add a secondary Y Axis - any help with that would be appreciated!</p>
  
  <p>Thanks.</p>