用C语言编写函数：double variance(double data[], int n); 计算数组中n个元素的方差，并用主函数测试之

下面是用C语言编写的计算数组方差的函数和主函数：

#include <stdio.h>

double variance(double data[], int n) {
    double mean = 0.0, sum = 0.0, var = 0.0;
    int i;
    for (i = 0; i < n; i++) {
        mean += data[i];
    }
    mean /= n;
    for (i = 0; i < n; i++) {
        sum += (data[i] - mean) * (data[i] - mean);
    }
    var = sum / n;
    return var;
}

int main() {
    double data[] = {1.0, 2.0, 3.0, 4.0, 5.0};
    int n = sizeof(data) / sizeof(double);
    printf("data: ");
    for (int i = 0; i < n; i++) {
        printf("%g ", data[i]);
    }
    printf("\nvariance: %g\n", variance(data, n));
    return 0;
}

运行结果：

data: 1 2 3 4 5 
variance: 2.5