title: hittest in polar chart with multiple series
body: <p>I have a polar chart with multiple series. I want to have a functionality to click on one of the datapoints in any series and perform something. I tried to use the HitTest and it works on a single series. The problem is when I used in on a chart with multiple series and sometimes when I click on a datapoint, it returns a different point. Please help.</p>
  
  <p>This is the snippet that I used.</p>
  
  <pre><code>HitTestResult result = chart1.HitTest(e.X, e.Y, ChartElementType.DataPoint);
  if (result.ChartElementType == ChartElementType.DataPoint)
  {
      var xVal = result.Series.Points[result.PointIndex].XValue;
      var yVal = result.Series.Points[result.PointIndex].YValues;
      result.Series.Points[result.PointIndex].MarkerColor = Color.Black;
  }
  </code></pre>
  
  <h1>update:</h1>
  
  <p>Thanks you so much for bearing with me. Anyway, this is the code incorporating what you suggested. </p>
  
  <pre><code>DataPoint dpCurrent = null;
      int normalMarkerSize = 10;
      int largeMarkerSize = 15;
  
      private void chart1_MouseClick(object sender, MouseEventArgs e)
      {
          HitTestResult result = chart1.HitTest(e.X, e.Y, ChartElementType.DataPoint);
          if (result.ChartElementType == ChartElementType.DataPoint)
          {
              dpCurrent = result.Series.Points[result.PointIndex];
              if (distance(PolarValueToPixelPosition(dpCurrent, chart1, result.ChartArea), e.Location) &lt;= 5)
                  result.Series.Points[result.PointIndex].MarkerColor = Color.Black;
          }
      }
  </code></pre>
  
  <p>However, I noticed that the value of "phi" in the PolarValueToPixelPosition is always returning NaN</p>