title: How to show multiple graphs in drilldown (highcharts)?
body: <p>NET MVC Project, where I use Highcharts. In my charts i have columns and a spline.</p>
  
  <p>I have already implemented drilldown for my chart and it works perfectly, but only for the columns. On the first level the columns and the spline is shown, but when I trigger drilldown only the columns are shown. data2 should be the spline.</p>
  
  <pre><code>var mychart = Highcharts.chart('container', {
                      chart: {
                          zoomType: 'xy',
                          spacingBottom: 40,
                          spacingTop: 40,
                          events: {
                              // DRILLDOWN
                              drilldown: function (e) {
  
      //Some variables id, func                            
  
  $.getJSON(`/Home/GetDataForMinuteDrilldown?id=${id}&amp;function=${func}`, function (data) {
                                          console.log(data);
  
                                          var durationArrMinutes = data.map(function (item) {
                                              return item['minuteavg'];
                                          });
  
                                          var errorArrayMinutes = data.map(function (item) {
                                              return item['errorsperminute']
                                          });
  
  
  
                                          var minuteArray = data.map(function (item) {
  
                                              return {
                                                  name: drill + ":" + item['minute'],
                                                  y: item['minuteavg'],
                                                  drilldown: item['minute']
                                              };
  
                                          });
  
                                          data2 = {
                                              name: 'Errors per Minute',
                                              type: 'spline',
                                              data: errorArrayMinutes,
                                              tooltip: {
                                                  valueSuffix: ' '
                                              }
                                          }
  
                                          data = {
                                              name: 'Average Duration per Minute',
                                              type: 'column',
                                              yAxis: 1,
                                              data: minuteArray,
                                              tooltip: {
                                                  valueSuffix: ' ms'
                                              },
                                              data2 //I think this is the error, but I i know no solution
                                          }
  
                                          console.log('Data:')
                                          console.log(data);
  
                                          mychart.hideLoading();
                                          mychart.addSeriesAsDrilldown(e.point, data);
                                      }); 
                              }
                          }
                      },
                      title: {
                          text: 'Performance and Error Analytics'
                      },
                      subtitle: {
                          text: 'Analytics of: ' + func
                      },
                      xAxis: [{
                          type: 'category',
                          crosshair: true
                      }],
                      yAxis: [{ // Primary yAxis
                          labels: {
                              format: '{value}',
                              style: {
                                  color: Highcharts.getOptions().colors[1]
                              }
                          },
                          title: {
                              text: 'Errors',
                              style: {
                                  color: Highcharts.getOptions().colors[2]
                              }
                          }
                      }, { // Secondary yAxis
                          title: {
                              text: 'Duration in ms',
                              style: {
                                  color: Highcharts.getOptions().colors[0]
                              }
                          },
                          labels: {
                              format: '{value} ms',
                              style: {
                                  color: Highcharts.getOptions().colors[0]
                              }
                          },
                          opposite: true
                      }],
                      tooltip: {
                          shared: true
                      },
                      legend: {
                          layout: 'vertical',
                          align: 'center',
                          x: 0,
                          verticalAlign: 'bottom',
                          y: 50,
                          floating: true,
                          backgroundColor:
                              Highcharts.defaultOptions.legend.backgroundColor || // theme
                              'rgba(255,255,255,0.25)'
                      },
                      series: [{
                          name: 'Average Duration per Hour',
                          type: 'column',
                          yAxis: 1,
                          data: durationPerHourArray,
                          tooltip: {
                              valueSuffix: ' ms'
                          }
                      }, {
                          name: 'Errors',
                          type: 'spline',
                          data: errorArray,
                          tooltip: {
                              valueSuffix: ' '
                          }
                      }],
                      drilldown: {
                          activeAxisLabelStyle: {
                              textDecoration: 'none',
                              fontStyle: 'normal',
                              color: 'black'
                          },
                          series: []
                      }
                  });
  </code></pre>