package com.company;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Daniel on 2018-03-03.
 */
public class Main {

    public static void main(String[] args) {


        List<Double> x = new ArrayList<Double>();
        List<Double> y = new ArrayList<Double>();
        x.add(1.0);
        x.add(2.0);
        x.add(3.0);
        x.add(4.0);
        y.add(1.0);
        y.add(4.0);
        y.add(9.0);
        y.add(16.0);




        double punkt = 15;
        double wartosc = lagrangeInterpolation(x,y,punkt);
        System.out.println("W punkcie "+punkt+" wartość "+ wartosc);

    }

    public static double lagrangeInterpolation(List xs, List ys, double x ){
        double t;
        double y = 0.0;

        for(int k = 0; k< xs.size(); k++){
            t = 1.0;
            for(int j = 0; j < xs.size() ; j++){
                if(j != k ){
                    double a = (Double) xs.get(j);
                    double b = (Double) xs.get(k);


                    t=t*((x-a)/(b-a));
                }
            }
            double c = (Double) ys.get(k);
            y += t*c;
        }
        return y;
    }
}