title: Custom Notation in HighChart series
body: <p>I have a section in my webpage, in which I show a <code>HighChart</code> graph, something as below:</p>
  
  <pre><code>Highcharts.chart('container', {
      chart: {
          type: 'line'
      },
      title: {
          text: 'Monthly Average Temperature'
      },
      subtitle: {
          text: 'Source: WorldClimate.com'
      },
      xAxis: {
          categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
      },
      yAxis: {
          title: {
              text: 'Temperature (°C)'
          }
      },
      plotOptions: {
          line: {
              dataLabels: {
                  enabled: true
              },
              enableMouseTracking: true
          }
      },
      series: [{
          name: 'London',
          data: [3.9, 4.2, 5.7, 8.5, 11.9, 15.2, 17.0, 16.6, 14.2, 10.3, 6.6, 4.8]
      }]
  });
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ZaCRj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZaCRj.png" alt="enter image description here"></a></p>
  
  <p>We can see that the points are displayed as <code>numbers</code>.
  I want that the numbers be replaced by <code>strings</code> such as <strong>'3.9%','4.2%'</strong>..and so on.</p>
  
  <p>When I change the data <code>array</code> in the above code to include the '%' sign, the chart doesn't render. I guess <code>HighCharts.js</code> only allows numbers to be plotted.</p>
  
  <p>How can the custom notation of <strong>'3.9%','4.2%'</strong>.. and so on be shown in the chart?</p>
  
  <p>Experts please help.</p>
  
  <p>Thanks</p>