c# OxyPlot coloring the graph under the curve

Question

Is it possible in OxyPlot to colour the graph under the curve? And if it is then how? Just like this

This is my source:

PlotView myPlot = new PlotView();
// Create Plotmodel object          
var myModel = new PlotModel { Title = string.Format("{0}\n\r∫f(x) = ({1}x^3) + ({2}x^2) + ({3}x) + ({4}) = {5} \n\r{6} ", horniMez, koeficienty[3], koeficienty[2], koeficienty[1], koeficienty[0], integral, dolniMez )};
           
myModel.Series.Add(new FunctionSeries(x=>koeficienty[3]*x*x*x+koeficienty[2]*x*x+koeficienty[1]*x+ koeficienty[0], dolniMez, horniMez, 0.1, string.Format( "Funkce: ({0}x^3) + ({1}x^2) + ({2}x) + ({3})", koeficienty[3], koeficienty[2], koeficienty[1], koeficienty[0])));

// Assign PlotModel to PlotView
myPlot.Model = myModel;

//Set up plot for display
myPlot.Dock = System.Windows.Forms.DockStyle.Top;
myPlot.Location = new System.Drawing.Point(0, 0);
myPlot.Size = new System.Drawing.Size(700, 700);
myPlot.TabIndex = 0;
Controls.Add(myPlot);

Thanks for any advice.

Answer 1

You can use an AreaSeries for this. An AreaSeries has two lists of points: Points for the upper edge and Points2 for the lower edge of an area. The area in between is filled with a color that you can specify using the Fill property. If no value is assigned for Points2, you can use this series to fill the area between the the x-axis and the points. You can also combine FunctionSeries with AreaSeries and use the first to calculate the points:

...

FunctionSeries function = new FunctionSeries(x=>koeficienty[3]*x*x*x+koeficienty[2]*x*x+koeficienty[1]*x+ koeficienty[0], dolniMez, horniMez, 0.1, string.Format( "Funkce: ({0}x^3) + ({1}x^2) + ({2}x) + ({3})", koeficienty[3], koeficienty[2], koeficienty[1], koeficienty[0])));

AreaSeries areaSeries = new AreaSeries();
areaSeries.Points.AddRange(functionSeries.Points);
areaSeries.Color = OxyColors.Black;                      // upper line color
areaSeries.Color2 = OxyColors.Black;                     // lower line, i.e. y=0
areaSeries.Fill = OxyColor.FromArgb(64, 255, 228, 181);  // fill color between
areaSeries.StrokeThickness = 1;

myModel.Series.Add(areaSeries);