牛顿插值 数值计算 java 代码 画函数图象

package test; import java.awt.Dimension; import java.awt.Graphics; import javax.swing.JFrame; import javax.swing.JPanel; public class test7 { //牛顿差值算法，得到方程的解，即多项式的系数 public static double[] niudun(double[] t, int n,double[] y) { double A[][] = new double[n + 1][n + 1]; double x[] = new double[n + 1]; t[0] = t[1] - 1; for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) A[i][j] = 1; for (int j = 2; j <= n; j++) { for (int i = j; i <= n; i++) { int k = j; while (k >= 2) { A[i][j] = A[i][j] * (t[i] - t[k - 1]); k--; } } } // 解下三角 for (int i = 1; i <= n; i++) x[i] = y[i]; // 求解 for (int i = 1; i <= n; i++) { x[i] = x[i] / A[i][i]; for (int j = i + 1; j <= n; j++) x[j] = x[j] - x[i] * A[j][i]; } // 输出解 System.out.println("牛顿法 方程的解（多项式系数）："); for (int j = 1; j <= n; j++) { System.out.println(x[j]); } System.out.println(); System.out.println(); return x; } public static void main(String args[]) { int n = 6; double t[] = { 0, 0, 0.5, 1.0,6.0,7.0,9.0 }; double y[] = { 0, 0, 1.6, 2.0,2.0,1.5,0.0}; double x[] = niudun(t,n,y); double b[] = new double[22]; //得到点坐标 用于画函数图象 System.out.println("选取点坐标为："); for(int i=0;i<=18;i++){ double j = i/2.0; b[i] = x[1] + x[2]*(j-t[1]) + x[3]*(j-t[1])*(j-t[2]) + x[4]*(j-t[1])*(j-t[2])*(j-t[3]) + x[5]*(j-t[1])*(j-t[2])*(j-t[3])*(j-t[4]) + x[6]*(j-t[1])*(j-t[2])*(j-t[3])*(j-t[4])*(j-t[5]) ; System.out.println("（"+j+" , "+b[i]+")"); } //通过窗口面板显示函数图象 JFrame jf = new JFrame("函数图象"); jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); MyPanel jp = new MyPanel(b,19); jp.setPreferredSize(new Dimension(900,300)); jf.getContentPane().add(jp); jf.setLocation(100, 100); jf.pack(); jf.setVisible(true); } } //窗口面板类 class MyPanel extends JPanel{ private static final long serialVersionUID = 1L; private int x=50; private int y=200; private int n; private double a[] = new double[50]; //构造函数 接收点坐标 public MyPanel(double[] b,int nn){ n = nn; for(int i=1;i<=n;i++) a[i] = b[i]; } //画出函数图象 public void paintComponent(Graphics g){ g.drawLine(x, y-150, x, y); g.drawLine(x, y, x+800, y); for(int i=0;i<n-1;i++) g.drawLine(x+i*40, (int) (y-a[i]*40), x+(i+1)*40, (int) ((int) y-a[i+1]*40)); } }