work1.cpp

作业: 最小二乘法 运行环境：vc 程序语言：c++ 程序源代码：work1.cpp （见附件）

// work1.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "stdio.h"
#include "math.h"
#include "iostream.h"
#define  MAX_N 25

struct point_type
{ 
	double x;
	double y;
	double weight;
	
}point[MAX_N];

int main(int argc, char* argv[])
{
	int n;
	int i;
	static double u11,u12,u21,u22,c1,c2;
	double a,b;
//
//输入数据的个数
	cout<<"输入点个数n:"<<endl;
	cin>>n;
//确认输入的数在正确输入范围
	while ((n>MAX_N)||(n<0))
	{
		cout<<"输入点个数必须在范围 1 到"<<MAX_N<<endl;
		cout<<"重新输入n:";
	    cin>>n;
	}
//输入数据
	
	cout<<"输入x_i,y_i,weight_i,i=0.."<<n-1<<": "<<endl;   
	for (i=0;i<n;i++)
		{		 
		    cin >>point[i].x>>point[i].y >>point[i].weight;

		}
	
	cout<<"输出x_i,y_i,weight_i,i=0.."<<n-1<<": "<<endl;   
	for (i=0;i<n;i++)
		{		 
		    cout<<point[i].x<<" "<<point[i].y <<" "<<point[i].weight<<endl;

		}
//方程组的求解
    u11=u12=0;
    u22=0;
    c1=c2=0;
    for (i=0;i<n;i++)
		{
			u11=u11+point[i].weight;
			u12=u12+point[i].weight*point[i].x;
			u22=u22+point[i].x*point[i].x*point[i].weight;
			c1=c1+point[i].y*point[i].weight;
			c2=c2+point[i].x*point[i].y*point[i].weight;

		}
	u21=u12;
 //求出线性函数系数   
	a=(c1*u22-c2*u12)/(u11*u22-u12*u21);
	b=(c1*u21-c2*u11)/(u21*u12-u22*u11);
	cout<<"解为 p(x):"<<a<<"+"<<b<<"x"<<endl;
	return 0;  
}