How do I graph a custom function in OxyPlot?

Question

I'm trying to graph a trend line for my data. Is there anyway to define a custom function? The closest I've seen is with in the Hello Windows Forms example here: http://www.oxyplot.org/doc/HelloWindowsForms.html

Code:

namespace WindowsFormsApplication1
{
    using System;
    using System.Windows.Forms;

    using OxyPlot;
    using OxyPlot.Series;

    public partial class Form1 : Form
    {
        public Form1()
        {
            this.InitializeComponent();
            var myModel = new PlotModel("Example 1");
            myModel.Series.Add(new FunctionSeries(Math.Cos, 0, 10, 0.1, "cos(x)"));
            this.plot1.Model = myModel;
        }
    }
}

In the example, they use Cosine. What if I needed to define a custom multivariable equation?

Edit: I've found a partial answer.

Use a Lambda series:

new FunctionSeries( x => a*x*x*x + b*x*x + c*x + d, .... )

Src: https://oxyplot.codeplex.com/discussions/439064

Still don't know how to do a multivariable equation though.

Answer 1

Here are the example picture: And this is the code:

    //your function based on x,y
    public double getValue(int x, int y)
    {
        return (10 * x * x + 11 * x*y*y  + 12*x*y );
    }

    //setting the values to the function
    public FunctionSeries GetFunction()
    { 
        int n = 100;
        FunctionSeries serie = new FunctionSeries();
        for (int x = 0; x < n; x++)
        {
            for (int y = 0; y < n; y++)
            {
                //adding the points based x,y
                DataPoint data = new DataPoint(x, getValue(x,y));

                //adding the point to the serie
                serie.Points.Add(data);
            }
        }
        //returning the serie
        return serie;
    }

    //setting all the parameters of the model
    public void graph()
    {
        model = new PlotModel { Title = "example" };
        model.LegendPosition = LegendPosition.RightBottom;
        model.LegendPlacement = LegendPlacement.Outside;
        model.LegendOrientation = LegendOrientation.Horizontal;

        model.Series.Add(GetFunction());
        var Yaxis = new OxyPlot.Axes.LinearAxis();
        OxyPlot.Axes.LinearAxis XAxis = new OxyPlot.Axes.LinearAxis { Position = OxyPlot.Axes.AxisPosition.Bottom, Minimum = 0, Maximum = 100 };
        XAxis.Title = "X";
        Yaxis.Title = "10 * x * x + 11 * x*y*y  + 12*x*y";
        model.Axes.Add(Yaxis);
        model.Axes.Add(XAxis);
        this.plot.Model = model;
    }

    //on click on the button 3 then show the graph
    private void button3_Click(object sender, EventArgs e)
    {
        graph();
    }