Example: The cubic spline interpolant with periodic boundary conditions

import com.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.*Math.PI/15./10.;
        for (int k = 0;  k < n;  k++) {
            x[k] = h * (double)(k);
            y[k] = Math.sin(15.0*x[k]);
        }
        
        CsPeriodic cs = new CsPeriodic(x, y);
        double csv =  cs.value(0.23);
        System.out.println("The computed cubic spline value at point .23 is "
        + csv);
    }
}

Output

The computed cubic spline value at point .23 is -0.3034014726064514