1.计算标准偏差C时的#QNAN0输出 [英] 1.#QNAN0 output when calculating standard deviation C

问题描述

我编写了一个用于计算标准偏差的函数，结果始终为"1.#QNAN0"，我尝试以其他方式设置其格式，但找不到解决方案.昨天它在另一台计算机上工作，我能做些什么吗?

I've written a function for calculating the standard deviation and the result is always '1.#QNAN0', I've tried formatting it in different ways but I can't find a solution. It was working on a different computer yesterday, is there anything I can do?

void CalcStandardDeviation(int count, int* nums, double mean, FILE* output){
    int k;
    double std=0,a;
    for (k=0; k<count; k++){
        a=nums[k]-mean;
        std=std+(a*a);
    }
    std/=(count);
    std=sqrt(std);
    fprintf(output,"Standard deviation: %f\r\n",std);
    fprintf(output,"\r\n");
   }

推荐答案

一个 NaN 只能您的代码中包含三个起源:

A NaN can only have three origins in your code:

• mean是 NaN .
• 在std/=(count);中，如果count为 0 .
• 在std=sqrt(std);中，如果std此时为负数(在您的情况下似乎不可能).

• mean is a NaN.
• In std/=(count); if count is 0.
• In std=sqrt(std); if std at this point is a negative number (seems impossible in your case).

您应该调试代码，并观察count和mean值(或打印/导出)以查找原因.

You should debug your code and watch count and mean values (or print/export it) to find the why.

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