Linechart over stream of numbers

Mar 29, 2012 at 11:02 AM

I'd like to make a linechart over a stream of numbers that continuously get's generated. Sort of like a cpu-usage graph or something along those lines; where the new data enters on the right side, and the old data exits on the left. Also, I do not know beforehand the maximum number that will be generated in this series (but I do know it will never be below 0). What I tried so far was something like this:

        private class NetworkPlotModel : PlotModel
            private LineSeries ups, downs;
            private LinearAxis vax;
            public NetworkPlotModel()
                Axes.Add(new TimeSpanAxis(pos: AxisPosition.Bottom, title: "Time", min: -60, max: 0));
                Axes.Add(vax = new LinearAxis(AxisPosition.Right, "Value"));
                vax.MaximumPadding = 0.03;

                Series.Add(ups = new LineSeries(OxyColor.FromRGB(1, 0, 0), strokeThickness: 3, title: "Up"));

            public void Push(TimeSpan delta, double up)
                for (int i = 0; i < ups.Points.Count; i++)
                    IDataPoint p = ups.Points[i];
                    ups.Points[i] = new DataPoint(p.X - delta.TotalSeconds, p.Y);
                ups.Points.Add(new DataPoint(0, up));

However, this does not seem to draw a line at all (even though I call the Push-method 1 time, 100 times or 1000 times, and I've also tried to call it once a sec, and up to 10 times a second).

Could I please get an example of how to make something like this work?

Mar 29, 2012 at 12:36 PM

I implemented something similar using an observable. Here is the code below, which might give you a few hints.

Random rand = new Random();

Observable.Interval(TimeSpan.FromSeconds(0.1)).Where( x => x < 100).Subscribe( x => 
			var series = ((LineSeries) pm.Series[0]);
			if( x > 50)
				// Remove the first point in the series when we readh 50 data points.
				// Reset the minimum value on the xAxis.
				pm.Axes[0].Minimum = series.Points[0].X;
			// Add the new point
			series.Points.Add( new DataPoint(3 + x, rand.Next(10)));
			// Set maximum value
			pm.Axes[0].Maximum = x;
			// Need to reset the xAxis for it refresh properly
			((LineSeries) pm.Series[0]).XAxis.Reset();


I think the PlotModel class also has a .Refresh() method.

Mar 30, 2012 at 11:16 AM

PlotModel.Update updates the model, but does not refresh the plot control.

Use PlotControl.Refresh or PlotModel.Refresh to redraw the plot.

Will add examples on the wiki page

Mar 30, 2012 at 11:47 AM

Thank you :)