title: Highcharts step line with gaps and series like [x,y]
body: <p>I'm trying to generate a line plot in Highcharts similar to this:</p>
  
  <pre><code>|---------------|
       |-----|
            |--------------|
                                      |-------|
                                          |------|
  </code></pre>
  
  <p>A sample series data has the following shape:</p>
  
  <pre><code>[{"name":"AA01", "data": [[1423102786000,37],[1423102786000,37],[1423124408000,118],[1423124408000,118],[1423139198000,0],[1423139198000,0],[1423139305000,0],[1423139305000,0],[1423139305000,48],[1423139305000,48],[1423142136000,15],[1423142136000,15],[1423147902000,37],[1423147902000,37],[1423153292000,0],[1423153292000,0],[1423461724000,43],[1423461724000,43],[1423461724000,89],[1423461724000,89],[1423461724000,52],[1423461724000,52],[1423461724000,4],[1423461724000,4],[1423461724000,5],[1423461724000,5],[1423480654000,10],[1423480654000,10],[1423480953000,0],[1423480953000,0]]}]
  </code></pre>
  
  <p>The x axis is an integer while the y axis is a date. As you can see, all data points go in pairs to get the above layout: the value in y axis is two consecutives times the same, while it changes only in the x axis date.
  I've followed some links to achieve this with no success:</p>
  
  <p><a href="https://stackoverflow.com/questions/23243386/highcharts-highstock-step-line-with-gaps">Link1</a></p>
  
  <p><a href="http://jsfiddle.net/gh/get/jquery/1.7.2/highslide-software/highcharts.com/tree/master/samples/highcharts/plotoptions/line-step/" rel="nofollow noreferrer">Link2</a></p>
  
  <p><a href="https://stackoverflow.com/questions/16516683/highstocks-line-missing-but-data-is-there">Link3</a></p>
  
  <p>As you can see, the main difference between these examples and my code is that I don't have a fixed categories axis, and that forces me to add the series data as <code>[x,y]</code> pairs.
  I've tried things like <code>[x,null]</code>, <code>[null,null]</code> and just <code>null</code> but all of them produced unexpected results, mainly with the x axis labels (showing as initial label <code>01-01-1970</code>) and zooming problems (when I zoom on an area with points it suddenly appears on around <code>01-01-1970</code>). This makes me think that Highcharts is assuming <code>01-01-1970</code> when a date is null, which messes the entire chart. This is my code, although it's quite simple anyway:</p>
  
  <pre><code>function plot(unit, data) {
                  $("#chart" + unit).highcharts({
                      credits: {
                          enabled: false
                      },
                      chart: {
                          zoomType: 'xy'
                      },
                      title: {
                          text: unit
                      },
                      xAxis: {
                          title: {
                              text: 'Date'
                          },
                          type: 'datetime',
                          labels: {
                              format: '{value:%Y-%m-%d}',
                              rotation: 45,
                              align: 'left'
                          },
                      },
                      yAxis: {
                          min: 0,
                          title: {
                              text: 'Event number'
                          }
                      },
                      legend: {
                          enabled: false
                      },
                      tooltip: {
                          formatter: function () {
                              return '&lt;b&gt;' + convertDate(new Date(this.x)) + '&lt;/b&gt;&lt;br/&gt;' +
                                      this.series.name + ': ' + this.y + '&lt;br/&gt;' +
                                      'Total: ' + this.point.stackTotal;
                          }
                      },
                      //plotOptions: {},
                      series: data
                  });
              }//END_FUNCTION
  </code></pre>
  
  <p>Could anyone help with this?</p>