I'm using the built in NDataZoomTool to zoom, but it is an incredible amount of data and hence, slow. I'd like to use my database to filter out records based on a given zoom level. How do I either create new lines or update the lines' values based on the result of a zoom operation?

Hi Mark,

You can use the EndDrag event and add only the data thats contained in the calculated axis range. The following code example shows how to achieve this:

  double[] m_xValues = new double[1000];
  double[] m_yValues = new double[1000];

  private void Form1_Load(object sender, EventArgs e)
  {
   NCartesianChart chart = (NCartesianChart)nChartControl1.Charts[0];
   NRangeSelection rs = new NRangeSelection();
   chart.RangeSelections.Add(rs);

   NPointSeries point = new NPointSeries();
   Random rand = new Random();
   point.DataLabelStyle.Visible = false;
   point.UseXValues = true;

   // generate some dummy data
   for (int i = 0; i < 1000; i++)
   {
    m_xValues[i] = rand.Next(1000);
    m_yValues[i] = rand.Next(1000);
   }

   // feed data to point series
   point.XValues.AddRange(m_xValues);
   point.Values.AddRange(m_yValues);

   chart.Series.Add(point);

   chart.Axis(StandardAxis.PrimaryX).View = new NRangeAxisView(new NRange1DD(0, 1000), true, true);
   chart.Axis(StandardAxis.PrimaryY).View = new NRangeAxisView(new NRange1DD(0, 1000), true, true);

   nChartControl1.Controller.Tools.Add(new NSelectorTool());

   NDataZoomTool dzt = new NDataZoomTool();
   dzt.EndDrag += new EventHandler(dzt_EndDrag);

   nChartControl1.Controller.Tools.Add(dzt);
  }

  void dzt_EndDrag(object sender, EventArgs e)
  {
   NCartesianChart chart = (NCartesianChart)nChartControl1.Charts[0];

   nChartControl1.Document.Calculate();
   nChartControl1.Document.RecalcLayout(nChartControl1.View.Context);

   NRange1DD yRange = chart.Axis(StandardAxis.PrimaryY).Scale.RulerRange;
   NRange1DD xRange = chart.Axis(StandardAxis.PrimaryX).Scale.RulerRange;

   AddDataInRange(xRange, yRange);
  }

  private void AddDataInRange(NRange1DD xRange, NRange1DD yRange)
  {
   NCartesianChart chart = (NCartesianChart)nChartControl1.Charts[0];
   NPointSeries point = (NPointSeries)chart.Series[0];
   point.XValues.Clear();
   point.Values.Clear();

   for (int i = 0; i < 1000; i++)
   {
    if (xRange.Contains(m_xValues[i]) && yRange.Contains(m_yValues[i]))
    {
     point.XValues.Add(m_xValues[i]);
     point.Values.Add(m_yValues[i]);
    }
   }
  }

Hope this helps - let us know if you have any questions or meet any problems.

Best Regards,
Nevron Support Team