aaa.cpp

这是我编的利用傅多项式插值计算法的程序。

#include <iostream.h>
#include <fstream.h>
#include <ostream.h>
#include <math.h>

double xx;
double y;
double P[11][12];

void main()
{	
	cout<<"对函数y=1/(1+25x^2)在以下点进行多项式插值"<<endl;
	cout<<"x=-1.0,-0.8,-0.6,-0.4,-0.2,0,0.2,0.4,0.6,0.8,1.0"<<endl;
	
	double x[12]={0,-1.0,-0.8,-0.6,-0.4,-0.2,0,0.2,0.4,0.6,0.8,1.0};
	double y[12]={0,1.0/26.0,1.0/17.0,0.1,0.2,0.5,1.0,0.5,0.2,0.1,1.0/17.0,1.0/26.0};
	//定义了十个点的坐标值

	for (int i=1;i<=11;i++)
	{
		P[0][i]=y[i];
		//cout<<P[0][i]<<endl;
	}
	//给叠代的起点赋值

	ofstream myfile;
	myfile.open("多项式插值数值.txt", ios::out);

	for (double step=0;step<=2000;step++ )
	{
		double xx=-1.0+0.001*step;
		
		for (int m=1;m<=10;m++)
		{
			for (int i=1;i+m<=11;i++)
			{
			     P[m][i]=((xx-x[i+m])*P[m-1][i]+(x[i]-xx)*P[m-1][i+1])/(x[i]-x[i+m]);
				 //cout<<P[m][i]<<endl;
			}
		}
		myfile<<xx<<"      ";
		myfile<<P[10][1]<<endl;
	}
}