/// <summary>
/// Compute an interpolated value from a set of known (x,y) values by Cubic Hermite Spline interpolation.
/// Extrapolation is NOT available.
/// </summary>
/// <param name="xArray">Array (row/column) of x-values.</param>
/// <param name="yArray">Array (row/column) of y-values.</param>
/// <param name="target">Value at which to compute the interpolation.</param>
/// <returns></returns>
public double CubicHermiteSplineInterpolate(double[] xArray, double[] yArray, double target)
{
if (xArray == null)
{
return(0);
}
if (yArray == null)
{
return(0);
}
var chsi = new CubicHermiteSplineInterpolation();
chsi.Initialize(xArray, yArray);//CubicSplineInterpolation.InterpolateAkima(xArray, yArray);
return(chsi.ValueAt(target, true));
}
public void TestFindBoundingInterval()
{
#region Test: Extrapolation at Left End Detected
_target = 273d;
try
{
_interpObj.ValueAt(_target, true);
}
catch (System.Exception e)
{
const string ErrorMessage =
"Cubic Hermite Spline does not support extrapolation";
Assert.AreEqual(ErrorMessage, e.Message);
}
#endregion Test: Extrapolation at Left End Detected
#region Test: Extrapolation at Right End Detected
_target = 5480.0001d;
try
{
_interpObj.ValueAt(_target, true);
}
catch (System.Exception e)
{
const string ErrorMessage =
"Cubic Hermite Spline does not support extrapolation";
Assert.AreEqual(ErrorMessage, e.Message);
}
#endregion Test: Extrapolation at Right End Detected
#region Test: Target Point at the Extreme Left
_target = 274d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(0m, _interpObj.LeftIndex);
Assert.AreEqual(1m, _interpObj.RightIndex);
#endregion Test: Target Point at the Extreme Left
#region Test: Target Point at the Extreme Right
_target = 5480d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(_xArray.Length - 2, _interpObj.LeftIndex);
Assert.AreEqual(_xArray.Length - 1, _interpObj.RightIndex);
#endregion Test: Target Point at the Extreme Right
#region Test: Target Point at the Second Knot Point
_target = 365d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(1, _interpObj.LeftIndex);
Assert.AreEqual(2, _interpObj.RightIndex);
#endregion Test: Target Point at the Second Knot Point
#region Test: Target Point at the Second Last Knot Point
_target = 3654d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(_xArray.Length - 2, _interpObj.LeftIndex);
Assert.AreEqual(_xArray.Length - 1, _interpObj.RightIndex);
#endregion Test: Target Point at the Second Last Knot Point
#region Test: Target Point Bounded by Second and Third Points
_target = 500d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(1, _interpObj.LeftIndex);
Assert.AreEqual(2, _interpObj.RightIndex);
#endregion Test: Target Point Bounded by Second and Third Points
#region Test:Target Point Bounded by Second and Third Last Points
_target = 3000d;
_interpObj.ValueAt(_target, true);
Assert.AreEqual(_xArray.Length - 3, _interpObj.LeftIndex);
Assert.AreEqual(_xArray.Length - 2, _interpObj.RightIndex);
#endregion Test:Target Point Bounded by Second and Third Last Points
}