C语言实现傅里叶变换算法详解

#include <stdio.h> #include <math.h>

#define PI 3.14159265358979323846

void fourier_transform(double x[], double y[], int n) { int i, j; double wr, wi, angle, tempr, tempi;

for (i = 0; i < n; i++) {
    x[i] = x[i] / n;
    y[i] = y[i] / n;
}

for (i = 0; i < n; i++) {
    tempr = 0.0;
    tempi = 0.0;
    angle = 2 * PI * i / n;

    for (j = 0; j < n; j++) {
        wr = cos(angle * j);
        wi = sin(angle * j);
        tempr += x[j] * wr - y[j] * wi;
        tempi += x[j] * wi + y[j] * wr;
    }

    x[i] = tempr;
    y[i] = tempi;
}

}

int main() { int i, n; double x[100], y[100];

printf("Enter the number of data points: ");
scanf("%d", &n);

printf("Enter the data points:

"); for (i = 0; i < n; i++) { scanf("%lf %lf", &x[i], &y[i]); }

fourier_transform(x, y, n);

printf("

Fourier transform: "); for (i = 0; i < n; i++) { printf("%lf + %lfi\n", x[i], y[i]); }

return 0;

}

此示例中，输入数据点并通过fourier_transform函数进行傅里叶变换，然后输出变换结果。请注意，此示例仅适用于离散傅里叶变换（DFT），并且需要在n个数据点上运行。