OxyPlot: How to calculate in TrackerFormatString?

I try to create a line series where not only x- and y-values shall be displayed in the tracker, but one more property:

var series = new LineSeries {TrackerFormatString = "X:{2}\nY:{4}\nZ:{2*(1-4)}"};
series.Points.AddRange(...);

I want another property Z = (1-Y) * X to be displayed in the third row of the tracker. How is this possible?

It is possible by creating a custom

public class CustomDataPoint : IDataPointProvider
{
        public double X { get; }
        public double Y { get; }
        public double Z{ get; }

        public CustomDataPoint(double x, double y)
        {
            X = x;
            Y = y;
            Z = (1 - Y) * X;
        }

        public DataPoint GetDataPoint()
        {
            return new DataPoint(X, Y);
        }
}

And then add it to the series:

var series = new LineSeries {TrackerFormatString = "X:{2}\nY:{4}\nZ:{Z}"};
series.ItemsSource = new [] {
    new CustomDataPoint(...),
    new CustomDataPoint(...)
};

Note that you need to use the ItemsSource property. You cannot simply add points with series.Point.AddRange(...).