如何使用C/C++来进行四参数Logistic曲线拟合四参数计算
时间: 2023-12-18 18:05:50 浏览: 48
下面是一个使用C++语言进行四参数Logistic曲线拟合的示例代码:
```c++
#include <iostream>
#include <cmath>
using namespace std;
double x[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
double y[] = { 1, 3, 4, 7, 10, 15, 20, 26, 32, 38 };
int n = 10;
double logistic(double x, double A, double B, double C, double D) {
return A + (B - A) / pow(1 + pow(C / x, D), D);
}
void four_param_fit(double *x, double *y, int n, double &A, double &B, double &C, double &D) {
double ym = y[0];
double xm = x[0];
for (int i = 1; i < n; i++) {
if (y[i] > ym) {
ym = y[i];
xm = x[i];
}
}
A = y[0];
B = ym;
C = xm;
D = 1;
double eps = 1e-8;
double err = 1;
while (err > eps) {
double A1 = A;
double B1 = B;
double C1 = C;
double D1 = D;
for (int i = 0; i < n; i++) {
double f = logistic(x[i], A, B, C, D);
double dfdA = 1;
double dfdB = 1;
double dfdC = (B - A) * D * pow(C, D) / pow(x[i] * C + pow(C, D), D + 1);
double dfdD = (B - A) * pow(x[i] * C, D) * log(x[i] * C) * pow(C, D) / pow(x[i] * C + pow(C, D), D + 1);
A1 += (y[i] - f) * dfdA;
B1 += (y[i] - f) * dfdB;
C1 += (y[i] - f) * dfdC;
D1 += (y[i] - f) * dfdD;
}
err = sqrt(pow(A1 - A, 2) + pow(B1 - B, 2) + pow(C1 - C, 2) + pow(D1 - D, 2));
A = A1;
B = B1;
C = C1;
D = D1;
}
}
int main() {
double A, B, C, D;
four_param_fit(x, y, n, A, B, C, D);
cout << "A = " << A << ", B = " << B << ", C = " << C << ", D = " << D << endl;
return 0;
}
```
该代码使用了最小二乘法进行四参数Logistic曲线拟合的计算,其中`four_param_fit`函数用于计算四个参数的值,`logistic`函数用于计算Logistic函数的值。在该示例代码中,输入数据为10个点的x和y值,输出为拟合得到的四个参数的值。