example5_9.java

清华大学2002年出版的《科学与工程数值计算算法Java》配套源码

import java.applet.*;
import java.awt.*;
public class Example5_9 extends Applet
{
 public double enaitken(double[] x,double[] y,double t,double eps)
 {int i,j,k,n=x.length;
  double f,l,dl;
  double[] p=new double[n];
  for(i=0;i<n-1;i++)
  {k=i;
   for(j=i+1;j<n;j++)if(Math.abs(t-x[j])<Math.abs(t-x[k])) k=j;
   if(k!=i)
   {f=x[k];x[k]=x[i];x[i]=f;f=y[k];y[k]=y[i];y[i]=f;}
  }
  p[0]=y[0];i=0;
  while(++i<n)
  {p[i]=y[i];
   for(j=0;j<i;j++)p[i]=((t-x[j])*p[i]-(t-x[i])*p[j])/(x[i]-x[j]);
   if(Math.abs(p[i]-p[i-1])<eps)break;
   }
  return p[i];
 }

 public void paint(Graphics g)
 {double[] x={0.10,0.15,0.30,0.45,0.55,0.60,0.70,0.85,0.90,1.00};
  double[] y=new double[10];
  double[] dy=new double[10];
  double f,t,eps=1e-7;int i;
  for(i=0;i<10;i++){y[i]=Math.sin(x[i]);dy[i]=Math.cos(x[i]);}
  for(i=0;i<5;i++)
  {t=Math.random();f=enaitken(x,y,t,eps);
   g.drawString("t="+t+"  f(t)="+f+"  实际值="+Math.sin(t),10,20+20*i);}
 }
}