用C++实现Excel的Slope函数

一个用C++实现的计算斜率的函数，跟Excel的Slope的计算结果一致，示例如下：

使用自定义C++函数计算结果如下：

完整代码如下：

#include <iostream>

#include <cstdio>

#include <vector>

using namespace std;

//判断double类型变量是否等于0

#define ISZERO(x) ((fabs(x) < 1e-6) ? true : false)

//计算斜率的函数

// @param vc：参与计算斜率的数字数组,从后向前取最新的nPeroid个数字计算

// @param nPeriod： 计算斜率的周期

double Slope(std::vector<double>& vc, int nPeriod)

{

?????? int sz = (int)vc.size();

?????? if (sz < nPeriod) { return 0; }

?????? double xsum = 0;

?????? double ysum = 0;

?????? double xxsum = 0;

?????? double xysum = 0;

?????? int i = 0, nBegin = sz - nPeriod;

?????? for (i = 0; i < nPeriod; ++i)

?????? {

????????????? xsum += i;

????????????? ysum += vc[nBegin + i];

????????????? xxsum += (1.0 * i) * i;

????????????? xysum += i * vc[nBegin + i];

?????? }

?????? double tmp = (xxsum - (xsum / nPeriod) * xsum);

?????? if (ISZERO(tmp)) { return 0; }

?????? return (xysum - (ysum / nPeriod) * xsum) / tmp;

}

//测试代码

int main()

{

?????? std::vector<int32_t> vc;

?????? vc.push_back(10);

?????? vc.push_back(11);

?????? vc.push_back(12);

?????? vc.push_back(13);

?????? vc.push_back(14);

?????? vc.push_back(15);

?????? vc.push_back(16);

?????? vc.push_back(16);

?????? vc.push_back(15);

?????? vc.push_back(14);

?????? vc.push_back(14);

?????? vc.push_back(12);

?????? vc.push_back(11);

?????? vc.push_back(11);

?????? vc.push_back(11);

?????? vc.push_back(10);

?????? vc.push_back(9);

?????? vc.push_back(8);

?????? vc.push_back(7);

?????? vc.push_back(6);

?????? vc.push_back(5);

?????? vc.push_back(4);

?????? vc.push_back(3);

?????? vc.push_back(2);

?????? vc.push_back(1);

??????

?????? std::vector<double> vcTmp;

?????? std::vector<double> vcSlope;

?????? for (size_t i = 0; i < vc.size(); ++i)

?????? {

????????????? vcTmp.push_back(vc[i]);

????????????? double dSlope = Slope(vcTmp, 4);

????????????? vcSlope.push_back(dSlope);

?????? }

?????? for (size_t i = 0; i < vcSlope.size(); ++i)

?????? {

????????????? printf("%-6d %-6d %.2lf\n", i, vc[i], vcSlope[i]);

?????? }

?????? return 0;

}