title: Dashed line for missing data in Chart.JS (spanGaps style)
body: <p>I have a chart with data points that are null. Chart.js does the correct thing and skips those data points but I would like to have a 'dashed' line fill in the missing parts. For example, in the below code the line should be solid as in the CodePen link, but should be dashed from "Blue" to "Yellow". I know the <code>spanGaps</code> option is available but I would like to apply a different style to it. </p>
  
  <p>Does anyone have any thoughts on how to accomplish this? I am using Chart.js 2.x</p>
  
  <pre><code>var ctx = document.getElementById("myChart");
  var myChart = new Chart(ctx, {
      type: 'line',
      data: {
          labels: ["Red", "Blue", "Orange", "Yellow"],
          datasets: [{
              label: '# of Votes',
              data: [12, 19, null, 3]
          }]
      },
      options: {
          scales: {
              yAxes: [{
                  ticks: {
                      beginAtZero:true
                  }
              }]
          }
      }
  });
  </code></pre>
  
  <p><a href="http://codepen.io/anon/pen/YNqwgx" rel="noreferrer">CodePen</a></p>