title: Highcharts tooltip formatter
body: <p>For <code>this.x</code>, I am getting the index location when I push the data in via code. If I populate the data separately, like the following code, then <code>this.x</code> returns the right item. How can I fix this issue?</p>
  
  <p><strong>Works</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>xAxis: {
      categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
  },
  
  series: [{
      data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]        
  }]
  </code></pre>
  
  <p><strong>Index location is getting pushed out for <code>this.x</code> here</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>var points = [{
      Name: 'good',
      Y: '15000'
  }, {
      Name: 'baad',
      Y: '3000'
  }, {
      Name: 'wow',
      Y: '2000'
  }];
  
  var chartData = {
      GetChartSeries: function (points, name) {
  
          var seriesData = [];
          if (points != null &amp;&amp; points != 'undefined') {
              for (i=0; i&lt;points.length; i++) {
                  seriesData.push({
                      name: ""+points[i].Name,
                      y: parseFloat(points[i].Y)
                      //,color: ''
                  });
              }
          }
          return seriesData;
      }
  };
  
  
  $(function () {
      $('#container').highcharts({
          chart: {
              type: 'column',
              margin: [ 50, 50, 100, 80],
              borderColor: '#A4A4A4',
              borderRadius: 5,
              borderWidth: 2
          },
          legend: { 
              enabled: false 
          },
          title: {
              text: 'Graduation Year Breakdown'
          },
          colors: ['#790000'],
          legend: {
              enabled: false
          },
          plotOptions: {
              series: {
                  /*
                  dataLabels: {
                      enabled: true,
                      color: 'red'
                  },
                  */
                  borderRadius: 3,
                  colorByPoint: true
              }
          },
          tooltip: {
              formatter: function() {
                  return '&lt;b&gt;'+ Highcharts.numberFormat(this.y, 0) +'&lt;/b&gt;&lt;br/&gt;'+
                      'in year: '+ this.x;
              }
          },
          xAxis: {
              categories: [],
              labels: {
                  rotation: -45,
                  align: 'right',
                  style: {
                      fontSize: '13px',
                      fontFamily: 'Verdana, sans-serif'
                  }
              }
          },
          yAxis: {
              min: 0,
              title: {
                  text: 'Number of Students'
              }
          },
          series: [{
              //name: 'Population',
              data: chartData.GetChartSeries(points, ""),//[4000, 3400, 2000, 34000, 120000],                 
              dataLabels: {
                  enabled: true,
                  //rotation: -90,
                  color: '#4F4F4F',
                  align: 'center',//'right',
                  //x: 4,
                  //y: 10,
                  style: {
                      fontSize: '12px',
                      //fontWeight: 'bold',
                      fontFamily: 'Verdana, sans-serif'
                  }
              }
  
          }]
      });
  });
  </code></pre>