Example: The cubic spline interpolant with periodic boundary conditions

using System;
using Imsl.Math;

public class CsPeriodicEx1
{
	public static void  Main(String[] args)
	{
		int n = 11;
		double[] x = new double[n];
		double[] y = new double[n];
		
		double h = 2.0 * System.Math.PI / 15.0 / 10.0;
		for (int k = 0; k < n; k++)
		{
			x[k] = h * (double) (k);
			y[k] = System.Math.Sin(15.0 * x[k]);
		}
		
		CsPeriodic cs = new CsPeriodic(x, y);
		double csv = cs.Eval(0.23);
		Console.Out.WriteLine("The computed cubic spline value at " +
			                  "point .23 is " + csv);
	}
}

Output

The computed cubic spline value at point .23 is -0.303401472606451