C++最小二乘计算线性回归方程

介绍

用来理解一下数学思路和练习一下代码。即兴而写的，所以没写注释。

代码

#include <iostream>
// #include "Windows.h"

double sum_square_x = 0;
double sum_x = 0;
double sum_y = 0;
double sum_xy = 0;
int n = 0;
double ave_x = 0;
double ave_y = 0;
double b_ba = 0;
double a_ba = 0;

using namespace std;

void InputAndSum()
{
    cout << "请输入n的值" << endl;
    cin >> n;
    cout << " " << endl;
    double data_x = 0;
    double data_y = 0;
    int i = 1;
    while (i <= n)
    {
        cout << "请输入第" << i << "个数据的x值" << endl;
        cin >> data_x;
        cout << " " << endl;
        cout << "请输入第" << i << "个数据的y值" << endl;
        cin >> data_y;
        cout << " " << endl;

        sum_x += data_x;
        sum_y += data_y;
        sum_xy += (data_x * data_y);
        sum_square_x += (data_x * data_x);
        
        i++;
    }

}

double Average(double a)
{
    double ave = a / n;
    return ave;
}

double B_ba(double calc1,double calc2)
{
    double square_ave_x = calc1 * calc1;
    double calc3;
    calc3 = (sum_xy - n * calc1 * calc2) / (sum_square_x - n * square_ave_x);
    return calc3;
}

void A_ba()
{
    a_ba = ave_y - b_ba * ave_x;
}

int main()
{
    InputAndSum();
    ave_x = Average(sum_x);
    ave_y = Average(sum_y);
    b_ba = B_ba(ave_x,ave_y);
    A_ba();
    cout << "---------------------------------" << endl;
    cout << "---------------------------------" << endl;
    cout << "n的值为： " << n << endl;
    cout << "各x的和为： " << sum_x << endl;
    cout << "各y的和为： " << sum_y << endl;
    cout << "各个xy乘积的求和为： " << sum_xy << endl;
    cout << "各个x平方的求和为： " << sum_xy << endl;
    cout << "x的均值为： " << ave_x << endl;
    cout << "y的均值为： " << ave_y << endl;
    cout << "a(ba)为： " << a_ba << endl;
    cout << "b(ba)为： " << b_ba << endl;
    cout << "样本点中心为：(" << ave_x << "," << ave_y << ")" << endl;
    cout << "回归直线方程为  y = " << b_ba << "x + " << "(" << a_ba << ")" << endl;
    cout << "---------------------------------" << endl;
    cout << "---------------------------------" << endl;
    //system("pause");

}