title: How to always show the plotLine in HighCharts?
body: <p>I am creating a HighChart with a plotLine in it. The plotLine has a fixed value, while the data can vary between charts.</p>
  <p>HighChart scales the y-axis automatically based on the maximum value of data, but it doesn't consider the plotLine's value in its calculations.</p>
  <p>Hence, if the data range encompasses the plotLine value, the plotLine gets shown, but gets cropped out of the viewport if not.</p>
  <p>Example:</p>
  <pre class="lang-js prettyprint-override"><code>    $(function () {
          $(document).ready(function() {
              var chart = new Highcharts.Chart({
                  chart: {
                      renderTo: 'container',
                      type: 'column'
                  },
                  title: {
                      text: 'Dummy Data by Region'
                  },
                  xAxis: {
                      categories: ['Africa', 'America', 'Asia']
                  },
                  yAxis: {
                      plotLines:[{
                          value:450,
                          color: '#ff0000',
                          width:2,
                          zIndex:4,
                          label:{text:'goal'}
                      }]
                  },
                  series: [{
                      name: 'Year 1800',
                      data: [107, 31, 650]
                  }]
              });
          });
          
      });​
  </code></pre>
  <p>JSFiddle for above code: <a href="http://jsfiddle.net/4R5HH/3/" rel="nofollow noreferrer">http://jsfiddle.net/4R5HH/3/</a></p>
  <p>The goal line (in red) is shown for the default data, but if I change the data to [107, 31, 250], then the plotLine goes out of the graph viewport and hence becomes invisible.</p>