public void CalculateTurningPointsTest()
{
//y = x*x + 2x -1
//y' = 2x +2
//Stationary point at x = - 1
List<DPoint> points = new List<DPoint>();
for (int i = -100; i < 101; i++)
{
double x = (double)i;
double y = x * x + 2 * x - 1;
points.Add(new DPoint(x, y));
}
StationaryPoints target = new StationaryPoints(points.ToArray());
TurningPoint[] actual;
actual = target.CalculateTurningPoints();
Assert.AreEqual(1, actual.Length);
Assert.IsFalse(actual[0].IsPeak);
Assert.AreEqual(-1d, actual[0].Point.X);
//Y = -2 at x = -1. Note turning point y value is NOT the differential
Assert.AreEqual(-2d, actual[0].Point.Y);
Assert.AreEqual(99, actual[0].Index);
}
public void CalculateTurningPointsTest2()
{
//y = x*x*x - x*x - x +1
//y' = 3x*x -2x -1 = (3x+1)(x-1)
//Stationary points solutions x = -1/3 (peak) , +1 (trough)
List<DPoint> points = new List<DPoint>();
for (double x = -10; x < 10; x=x+0.01)
{
double y = x * x * x - x * x - x + 1;
points.Add(new DPoint(x, y));
}
Differentiator differentiator = new Differentiator(points);
differentiator.SampleSize = 9;
DPoint[] diffPoints = differentiator.Differentiate();
StationaryPoints target = new StationaryPoints(points.ToArray(), diffPoints);
target.Threshold = 0;
TurningPoint[] actual;
actual = target.CalculateTurningPoints();
Assert.AreEqual(2, actual.Length);
Assert.IsTrue(actual[0].IsPeak);
Assert.AreEqual("-0.33", actual[0].Point.X.ToString("0.00"));
Assert.IsFalse(actual[1].IsPeak);
Assert.AreEqual("1.00", actual[1].Point.X.ToString("0.00"));
}