DUPA

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows.Forms.DataVisualization.Charting;

namespace Koniecznav3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Oblicz_Click(object sender, EventArgs e)
        {
            double xy = double.Parse(xxTB.Text);
            double wynik = 0;

            string s = xTB.Text;
            String[] split = s.Split(' ');
            double[] TabX = new double[split.Length];
            for (int i = 0; i < split.Length; i++)
            {
                TabX[i] = double.Parse(split[i]);
            }

            string s2 = yTB.Text;
            String[] split2 = s2.Split(' ');
            double[] TabY = new double[split2.Length];
            for (int i = 0; i < split2.Length; i++)
            {
                TabY[i] = double.Parse(split2[i]);
            }

            for(int i = 0; i < TabY.Length; i++)
            {
                wynik += L(TabX, xy, i) * TabY[i];
            }
            wynikTB.Text = wynik.ToString();
        }

        public double L(double [] x ,double xy, int indexL)
        {
            double wynik = 1;
            for(int i = 0; i < x.Length; i++)
            {
                if (i != indexL)
                {
                    wynik =wynik* ((xy - x[i]) / (x[indexL] - x[i]));
                }
            }
            return wynik;
        }

        private void rysuj_Click(object sender, EventArgs e)
        {
            double xy = double.Parse(xxTB.Text);

            string s = xTB.Text;
            String[] split = s.Split(' ');
            double[] TabX = new double[split.Length];
            for (int i = 0; i < split.Length; i++)
            {
                TabX[i] = double.Parse(split[i]);
            }

            string s2 = yTB.Text;
            String[] split2 = s2.Split(' ');
            double[] TabY = new double[split2.Length];
            for (int i = 0; i < split2.Length; i++)
            {
                TabY[i] = double.Parse(split2[i]);
            }

            var chart = chart1.ChartAreas[0];
            chart.AxisX.LabelStyle.Format = "";
            chart.AxisY.LabelStyle.Format = "";
            chart.AxisX.LabelStyle.IsEndLabelVisible = true;

            chart1.Series.Add("f(x)");
            chart1.Series["f(x)"].ChartType = SeriesChartType.Line;
            chart1.Series["f(x)"].Color = Color.Red;
            chart1.Series[0].IsVisibleInLegend = false;

            double wartoscX, wartoscY;
            for (wartoscX = TabX[0]; wartoscX <= TabX[TabX.Length - 1]; wartoscX += 0.01)
            {
                wartoscY = 0;
                for (int i = 0; i < TabX.Length; i++)
                {
                    wartoscY += L(TabX, wartoscX, i) * TabY[i];
                }
                chart1.Series["f(x)"].Points.AddXY(wartoscX, wartoscY);
            }
        }
    }
}