[英]Read values from a column in a file
我正在嘗試從特定列中的文件中讀取值(忽略第一個數字),然后找到該列的平均值。 到目前為止,我有這段代碼可用於讀取和查找行的平均值,但不適用於該列。
#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);
}
因此,在該文件中,共有5列,第一列是ID,它是just和interger值(整數),其他數字都是浮點數。
文件內容:
12345 60 30 63.2 95
54321 54.2 49 40.5 80
15243 99.5 100 90 98
您可以保留一個變量sum
來添加特定列的所有值,然后使用該值來獲取平均值,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) );
#include <stdio.h>
#include <stdlib.h>
int main(){
FILE *fp;
int id;
float mark1;
float mark2;
float mark3;
float mark4;
int number;
float somme[4];
int nbLg=0;
int i;
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){
nbLg++;
somme[0]+= mark1;
somme[1]+= mark2;
somme[2]+= mark3;
somme[3]+= mark4;
}
for(i=0;i<=3;i++) {
printf("Average for %d : %.2f\n", i+1, somme[i] / (float) nbLg);
}
fclose(fp);
}
以下代碼是:
稍加思考和紙//鉛筆工作就會給您類似的邏輯
#include <stdio.h>
#include <stdlib.h>
int main( void )
{
FILE *fp;
float mark1;
float mark1Average = 0.0f;
float mark2;
float mark2Average = 0.0f;
float mark3;
float mark3Average = 0.0f;
float mark4;
float mark4Average = 0.0f;
int number;
int numberAverage = 0;
fp= fopen("grades.txt", "r");
if(fp == NULL){
printf("File cannot be opened");
exit(-1);
}
// get first line to initialize average values
if ( 5 != fscanf( fp, "%d %f %f %f %f",
&numberAverage,
&mark1Average,
&mark2Average,
&mark3Average,
&mark4Average )
)
{ // then fscanf failed
perror( "fscanf for first line of grades.txt failed" );
exit( EXIT_FAILURE );
}
// implied else, fscanf successful
while(5 == fscanf(fp, "%d %f %f %f %f", &number, &mark1, &mark2, &mark3, &mark4 ))
{
numberAverage = (numberAverage+number)/2;
mark1Average = (mark1Average+mark1)/2.0f;
mark2Average = (mark2Average+mark2)/2.0f;
mark3Average = (mark3Average+mark3)/2.0f;
mark4Average = (mark4Average+mark4)/2.0f;
}
printf( "numberAverage: %d\n", numberAverage);
printf( "mark1Average: %f\n", mark1Average);
printf( "mark2Average: %f\n", mark2Average);
printf( "mark3Average: %f\n", mark3Average);
printf( "mark4Average: %f\n", mark4Average);
fclose(fp);
}
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