来源：http://blog.csdn.net/qll125596718/article/details/8248249
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求a、b的值：
// Ordinary Least Square.cpp : 定义控制台应用程序的入口点。
//
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#include
"stdafx.h"
#include
<iostream>
#include
<fstream>
#include
<vector>
using
namespace std;
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class LeastSquare
{
????double a, b;
public:
????LeastSquare(const vector<double>& x, const vector<double>& y)//最小二乘法公式
????{
????????double t1 = 0, t2 = 0, t3 = 0, t4 = 0;
????????for (int i = 0; i < x.size(); ++i)
????????{
????????????t1 += x[i] * x[i];
????????????t2 += x[i];
????????????t3 += x[i] * y[i];
????????????t4 += y[i];
????????}
????????a = (t3 * x.size() - t2 * t4) / (t1 * x.size() - t2 * t2);
????????b = (t1 * t4 - t2 * t3) / (t1 * x.size() - t2 * t2);
????}
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????double getY(const
double x) const
????{
????????return a * x + b;
????}
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????void print() const
????{
????????cout << "y = " << a << "x + " << b << endl;
????}
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};
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int _tmain(int argc, _TCHAR* argv[])
{
????if (argc != 2)
????{
????????cout << "Usage: DataFile.txt" << endl;
????????return -1;
????}
????else
????{
????????vector<double> x;
????????ifstream in(argv[1]);
????????for (double d; in >> d;)//将读取出来的数值全部存入容器X中
????????{
????????????x.push_back(d);//push_back()是把一个元素，放入这个容器的末尾，相当于末尾添加一个元素
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????????}
????????int sz = x.size();
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????????vector<double> y(x.begin() + sz / 2, x.end());//把余下的容器Ｘ中的元素全部放进容器Y
????????x.resize(sz / 2);//调整容器X的长度大小，超过当前size的元素删除
????????LeastSquare ls(x, y);//调用最小二乘法求a和b
????????ls.print();
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????????cout << "Input x:\n";
????????double x0;
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????????while (cin >> x0)
????????{
????????????cout << "y = " << ls.getY(x0) << endl;
????????????cout << "Input x:\n";
????????}
????}
????return 0;
}
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实验模拟数据：
|
10 |
15 |
20 |
25 |
30 |
35 |
40 |
45 |
|
2000.36 |
2000.50 |
2000.72 |
2000.80 |
2001.07 |
2001.25 |
2001.48 |
2001.60 |
实验结果：
