How do I plot real-time signal in WPF and C# .net 3.5?

Question

I am trying plot real-time signal, signal vs time, with WPF and C# (Dynamic Data Display); Once a signal is generated, it should be showed up on a plot chart instantly; The signal can be generated very fast (on the order of mili-second (0.001 second)); What would be the best way to do it? Any suggestion is appreciated.Thanks.

EDIT: An example code will be highly appreciated.

Here is what I have tried:

Plot initiation:

#region Constructor
public SignalStatsDisplay()
{
    InitializeComponent();

    plotter.Legend.Remove();

    _initialChildrenCount = plotter.Children.Count;

    int count = plotter.Children.Count;

    //do not remove the initial children
    if (count > _initialChildrenCount)
    {
        for (int i = count - 1; i >= _initialChildrenCount; i--)
        {
            plotter.Children.RemoveAt(i);
        }
    }

    _nColorChannels = 4;

    _lineprofileColor = new Color[4];

    _lineprofileColor[0] = Colors.Transparent;
    _lineprofileColor[1] = Colors.Red;
    _lineprofileColor[2] = Colors.Black;
    _lineprofileColor[3] = Colors.Blue;


    //LineGraph lg = new LineGraph();
    LineAndMarker<MarkerPointsGraph> lg = new LineAndMarker<MarkerPointsGraph>();
    CirclePointMarker pm = new CirclePointMarker { Size = 10, Fill = Brushes.Green };

  //  MarkerPointsGraph mpg = new MarkerPointsGraph();

    if (_nColorChannels > 0)    // plotter init
    {
        _dataX = new List<int[]>();
        _dataY = new List<int[]>();

        int[] dataXOneCh = new int[1];
        int[] dataYOneCh = new int[1];

        dataXOneCh[0] = 0;
        dataYOneCh[0] = 0;

        /*CirclePointMarker marker = new CirclePointMarker();
        marker.Fill = new SolidColorBrush(_lineprofileColor[0]);
        marker.Pen = new Pen(marker.Fill, 0);

        marker.Size = 2;
        int lineWidth = 1;*/




        for (int i = 0; i < 4; i++)
        {
            _dataX.Add(dataXOneCh);    // data x-y mapping init
            _dataY.Add(dataYOneCh);

            EnumerableDataSource<int> xOneCh = new EnumerableDataSource<int>(dataXOneCh);
            EnumerableDataSource<int> yOneCh = new EnumerableDataSource<int>(dataYOneCh);

            xOneCh.SetXMapping(xVal => xVal);
            yOneCh.SetXMapping(yVal => yVal);

            CompositeDataSource dsOneCh = new CompositeDataSource(xOneCh, yOneCh);

           // LineProfileColorSetup();

            lg = plotter.AddLineGraph(dsOneCh,                    
                (new Pen(Brushes.Green, 2)),
                 pm,
                (new PenDescription("Data")));

           // lg = plotter.AddLineGraph(dsOneCh,
           //    Colors.Transparent,
           //    2,
           //    "Data");

          // pm.FilteringEnabled = false;

        }

        plotter.FitToView();
    }
    else
    {
        return;
    }
}

Data update:

 for (int i = 0; i < 1; i++)
                {
                    if (_dataX[i].Length == _dataY[i].Length)
                    {
                        EnumerableDataSource<int> xOneCh = new EnumerableDataSource<int>(_dataX[i]);
                        xOneCh.SetXMapping(xVal => xVal);
                        EnumerableDataSource<int> yOneCh = new EnumerableDataSource<int>(_dataY[i]);
                        yOneCh.SetYMapping(yVal => yVal);
                        CompositeDataSource ds = new CompositeDataSource(xOneCh, yOneCh);

                        Action UpdateData = delegate()
                        {
                           // ((LineGraph)plotter.Children.ElementAt(startIndex + i)).DataSource = ds;
                           // ((LineGraph)plotter.Children.ElementAt(startIndex + i)).LinePen = new Pen(new SolidColorBrush(Colors.Green), 1);
                           // ((PointsGraphBase)plotter.Children.ElementAt(startIndex + i)).DataSource = ds;
                            ((PointsGraphBase)plotter.Children.ElementAt(startIndex + i + 1)).DataSource = ds;

                            //  }
                           // (plotter.Children.ElementAt(startIndex + i)).DataSource = ds; 

                        };

                        this.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal, UpdateData);
                    }
                }

The problem I have is when signal comes in very fats, say a new signal is generated every mili-second, it seems the graph only generate a new marker every 1 second, which I don't understand.

The basic idea is to generate a plotter.AddLineGraph, then only update the DataSource. But it seems not working. So I thought maybe I am on the wrong direction.

I am not a C# or WPF expert. When LineAndMarker does not work as expected, I started doubting. So I am wondering what would be the general way for people to display real-time signal (rapidly changing, time span between samples could be on mili-second) using WPF and C#.

Answer 1

I found where I did wrong. Here is the part where problem happens:

_pxlValAllChan[0, signalIndex] = pxlValue;
                                                DateTime currentTime = DateTime.Now; //has to come from real file: Tiff
                                                TimeSpan timeSpan = currentTime - _startTime;

                                                _timeStampAllChan[0, signalIndex] = Convert.ToInt16(timeSpan.TotalSeconds);


                                                _pxlValOneChan = new int[_signalLength]; // no need to new it every time
                                                _timeStampOneChan = new int[_signalLength];
                                                for (int i = 0; i <= signalIndex; i++)
                                                {
                                                    _pxlValOneChan[i] = _pxlValAllChan[0, i];
                                                    //_timeStampOneChan[i] = _timeStampAllChan[0, i];
                                                    _timeStampOneChan[i] = i;
                                                }

                                                _signalDisplay.SetData(_timeStampOneChan, _pxlValOneChan, 0, true);

My x data was based on time. I basically consider the initiation of program as starting point, then I keep track of time elapse by subtracting starting time with current time. Then the time elapse is saved as x-axis data (see the line that is commented out). And this actually causes problem. When I simple change x-axis data as index, the problem is gone. The graph update pretty fast. Although I have not figure out how I should change the logic to still use time elapse as my x-axis data, but that is the culprit of slow updating on the graph.