数值计算方法--插值函数(java实现)

import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.awt.geom.*; public class Interpolation extends Canvas{ /** * @插值 */ static int n=7; static double x[]={-3.0,-2.0,-1.0,0,1.0,2.0,3.0}; static double y[]=new double[n]; Interpolation(){ for(int i=0;i<n;i++) { y[i]=Math.sin(x[i]); } } @Override public void paint(Graphics g) { Graphics2D g_2d=(Graphics2D)g; zuobiao(g_2d); Interpolation.sinx(g_2d,0); Interpolation.sinx(g_2d,1); } public void zuobiao(Graphics2D g_2d){ //画出x轴 Line2D line=new Line2D.Double(50,150,450,150); g_2d.draw(line); Line2D line1=new Line2D.Double(250,30,250,280); g_2d.draw(line1); //画出箭头 Line2D line2=new Line2D.Double(445,155,455,150); g_2d.draw(line2); Line2D line3=new Line2D.Double(445,145,455,150); g_2d.draw(line3); Line2D line4=new Line2D.Double(255,35,250,25); g_2d.draw(line4); Line2D line5=new Line2D.Double(245,35,250,25); g_2d.draw(line5); g_2d.drawString("X", 460, 170); g_2d.drawString("Y", 230, 30); g_2d.setColor(Color.blue); g_2d.drawString("绿线--->sin(x)", 400, 30); g_2d.setColor(Color.red); g_2d.drawString("红线--->L(x)", 400, 50); } public static void sinx(Graphics2D g_2d,int i){ double y1=150; if(i==0) g_2d.setColor(Color.blue); else g_2d.setColor(Color.red); for(int x=80;x<=420;x++) { double y; if(i==0) y= Math.sin((x-250)/50.0); else y = L((x-250)/50.0); y=y1-y*50; g_2d.drawString(".",x,(int)y); } } public static double L(double x1){ double x2=0.0; for(int k=0;k<n;k++) { x2=x2+l(x1,k)*y[k]; } return x2; } public static double l(double x1,int k){ double x2=1.0,x3=1.0; for(int j=0;j<n;j++) { if(j!=k) { x2=x2*(x1-x[j]); x3=x3*(x[k]-x[j]); } } return x2/x3; } public static void main(String[] args) { JFrame f=new JFrame("三角函数图及近似图"); f.setBounds(100,100,500,350); f.setVisible(true); f.addWindowListener(new WindowAdapter(){ @Override public void windowClosing(WindowEvent e) { System.exit(0); } }); f.add(new Interpolation(),BorderLayout.CENTER); f.validate(); } }