chazhi.java

计算方法课

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.util.Random;
import java.lang.String;
import java.io.*;
public class chazhi extends Applet implements ActionListener{
  static int N=7;
  int minx, maxx;
  int[] x, y;
  Random ran = new Random();
  Button a, b, c, d, e;
  boolean choosea, chooseb, choosec, choosed, choosee;
  public void init() {

    x = new int[N + 1];
    y = new int[N + 1];
    a = new Button("随机产生点");
    b = new Button("拉格朗日");
    c = new Button("牛顿");
    d = new Button("样条");
    e = new Button("退出");
    add(a);add(b);add(c);add(d);add(e);
    a.addActionListener(this);
    b.addActionListener(this);
    c.addActionListener(this);
    d.addActionListener(this);
    e.addActionListener(this);
  }
  public void actionPerformed(ActionEvent ae) {
    String str = ae.getActionCommand();
    if (str.equals("随机产生点")) {
      choosea = true;chooseb=false;choosec=false;choosed=false;choosee=false;
      for (int i = 0; i <= N; i++) {
        x[i] = ran.nextInt(60) + i * 50 + 60;
        y[i] = ran.nextInt(50)+ 200-10*i;
      }
      minx = x[0];
      maxx = x[N];
      repaint();
    }
    if (str.equals("拉格朗日")) {
      chooseb = true;
      repaint();
    }
    if (str.equals("牛顿")) {
      choosec = true;
      repaint();
    }
    if(str.equals("样条")){
    	choosed=true;
    	repaint();
    }
    if(str.equals("退出")){
    	choosee=true;
    	repaint();
    }
  }
  public void paint(Graphics g) { //绘图
    g.drawLine(30, 350, 30, 30);
    g.drawLine(30, 350, 500, 350);
    g.drawLine(30, 30, 34, 39);
    g.drawLine(30, 30, 26, 39);
    g.drawLine(500, 350, 495, 345);
    g.drawLine(500, 350, 495, 355);
    g.drawString("x", 505, 360);
    g.drawString("y", 20, 32);
    g.drawString("0", 20, 355);
    g.setColor(Color.blue);
    g.drawLine(400, 60, 423, 60);
    g.drawString("lagrange", 425, 65);
    g.setColor(Color.red);
    g.drawLine(400, 80, 423, 80);
    g.drawString("newton", 425, 85);
    g.setColor(Color.green);
    g.drawLine(400, 100, 423, 100);
    g.drawString("spline", 425, 105);

    if (choosea) {
      for (int i = 0; i <= N; i++) {
        g.setColor(Color.black);
        g.drawOval(x[i] - 2, y[i] - 2, 4, 4); //像素较正
        g.fillOval(x[i] - 2, y[i] - 2, 4, 4);
        Point p=new Point(x[i]-30,350-y[i]);
        //String s=new String();              //坐标
        //s=p.toString();
        //g.setColor(Color.lightGray);
       //g.drawString(s,x[i]+4,y[i]+4 );
      }
    }
    if (chooseb) {
      g.setColor(Color.blue);
      float L, LI;
      int i, j, k;
      int m = x[0];
      int n = y[0];
      for (k = minx; k <= maxx; k++) {
        L = 0;
        for (i = 0; i <= N; i++) { //拉格朗日插值函数L=...
          LI = 1;
          for (j = 0; j <= N; j++) {
            if ( (j != i)) LI = LI * (k - x[j]) / (x[i] - x[j]);
          }
          L = L + LI * y[i];
        }
        g.drawLine(m, n, k, (int) L);
        m = k;
        n = (int) L;
      }
    }
    if (choosec) {
      g.setColor(Color.red);
      float[] f = new float[N + 1];
      float NewTon;float t;
      int k;
      int m = x[0];
      int n = y[0];
      for (k = minx; k <= maxx; k++) {
        for (int r = 0; r <= N; r++) {
          f[r] = y[r];
        }
        NewTon =y[0];
        t = 1;
        for (int j = 1; j <= N; j++) {
          t = t * (k - x[j - 1]);
          for (int i = 0; i <= N - j; i++)
          {
            f[i] = (f[i + 1] - f[i]) / (x[j + i] - x[i]);
          }
          NewTon = NewTon + f[0] * t;
        }
        g.drawLine(m, n, k, (int) NewTon);
        m = k;
        n = (int) NewTon;
      }
    }
     if(choosed)
	  {
		  g.setColor(Color.green);
		  float h[]=new float[N+1];float a[]=new float[N+1];
		  float c[]=new float[N+1];float d[]=new float[N+1];
		  float b[]=new float[N+1];float s2[]=new float[N+1];
		  float s1,s3;
		  for(int k=0;k<N;k++)
			  h[k]=x[k+1]-x[k];
		  a[1]=2*(h[0]+h[1]);
		  for(int k=2;k<N;k++)
			  a[k]=2*(h[k-1]+h[k])-(h[k-1]*h[k-1])/a[k-1];
		  for(int k=1;k<=N;k++)
			  c[k]=(y[k]-y[k-1])/h[k-1];
		  for(int k=1;k<N;k++)
			  d[k]=6*(c[k+1]-c[k]);
		  b[1]=d[1];
		  for(int k=2;k<N;k++)
			  b[k]=d[k]-b[k-1]*h[k-1]/a[k-1];
		  s2[N-1]=b[N-1]/a[N-1];
		  for(int k=N-2;k>0;k--)
			  s2[k]=(b[k]-h[k]*s2[k+1])/a[k];
		  s2[0]=0;s2[N]=0;
		  for (int k =0; k <= N; k++){
		  	int m=x[k];
		  	int n=y[k];
		  	for(int x1=x[k];x1<x[k+1];x1++){
			  	s1=c[k+1]-s2[k+1]*h[k]/6-s2[k]*h[k]/3;
	            s3=y[k]+s1*(x1-x[k])+s2[k]*(x1-x[k])*(x1-x[k])/2
	            +(s2[k+1]-s2[k])*(x1-x[k])*(x1-x[k])*(x1-x[k])/(6*h[k]);
                g.drawLine(m, n, x1, (int) s3);
                m = x1;
                n = (int)s3;
                }
           }
         }
         /*(choosee){
          exit(0);
         }*/
}}