c - 从文件中的列中读取值

Question

我正在尝试从文件中的特定列(忽略第一个数字)读取值，然后找到该列的平均值。到目前为止，我有这段代码可用于读取和查找行的平均值，但不适用于该列。

#include <stdio.h>
#include <stdlib.h>

int main(){

    FILE *fp;
    int id;
    float mark1;
    float mark2;
    float mark3;
    float mark4;
    int number;
    float average;

    fp= fopen("grades.txt", "r");

    if(fp == NULL){
        printf("File cannot be opened");
        exit(-1);
    }

    while(fscanf(fp, "%d %f %f %f %f", &number, &mark1, &mark2, &mark3, &mark4 ) != EOF){
        //code to calculate average and print output
        //Below is the code I used to find the average of the line (not what I want to do)
        average = (mark1 + mark2 + mark3+ mark4)/4;
        printf("Average for %d : %.2f\n", number, average);

    }

    fclose(fp);
}

所以在文件中一共有5列，第一列是刚好是整数的ID和整数值(int number)，其他的数字都是 float 。

文件内容:

12345 60 30 63.2 95
54321 54.2 49 40.5 80
15243 99.5 100 90 98 

Answer 1

您可以保留一个变量 sum 来添加特定列的所有值，然后使用它来获取平均值，例如

int sum=0, n=0;

while(fscanf(fp, "%d %f %f %f %f", &number, &mark1, &mark2, &mark3, &mark4 ) != EOF){
    //code to calculate average and print output
    //Below is the code I used to find the average of the line (not what I want to do)
    average = (mark1 + mark2 + mark3+ mark4)/4;
    printf("Average for %d : %.2f\n", number, average);

    sum += mark2 //this can be any mark depending on your requirement
    n++;         //this is to keep track of the number of lines

}

printf("the average of column 2 is %d", (sum/n) );