public static void Gauss2dTest()
{
// sample 2d normal distribution function from -10 to 10 with 201x201 samples
var range = 10;
var area = new Box2d(-range, -range, range, range);
var sampleCount = 201; // uneven values with give symmetrical pdf
var pdf = new Matrix <double>(sampleCount, sampleCount);
pdf.SetByCoord((x, y) =>
{
var px = x / (sampleCount - 1.0);
var py = y / (sampleCount - 1.0);
var p = area.Lerp(px, py);
return(Fun.Gauss2d(p.X, p.Y, 1.0));
});
// integrate sampled gauss distribution
var stepSize = range * 2.0 / (sampleCount - 1.0);
var integral = pdf.Data.Sum() * stepSize * stepSize;
// Gauss must integrate to 1.0
Assert.True(integral.ApproximateEquals(1.0, 1e-10));
}