Thread: help! reading from file and computing average

hello i am about a month into a computer programming 1 class at a university...i need to write a program that gets data from a file and computes the total number,average and max and min....i've started this program, but now im stuck. im not sure how the loop goes or if i even have the beginning part right...here is my code if anyone has any suggestions or hints i would really appreciate it. thanks

Code:

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

int main()
{
   int temp, ;
   int tempcount = 0;
   FILE *tempsIn;
   
   tempsIn = fopen("c:\\documents and settings\\desktop\\temps.txt", "r");
   
   printf("Temperature Analyzer v1.1\n");
   printf("\n");
   printf("What file to analyze?");
   
   if( tempsIn == NULL ) {
      printf("File could not be opened ... exiting.\n");
      system("pause");
      exit(EXIT_FAILURE);      // quit program
   }
   while(fscanf(tempsIn, "%2d%2lf", &temp);
      if ( 
   
   
   
   system("pause");
   return 0;
}

If you're going to use two format specifiers in your fscanf statement, you need two variables to put the information into.

For average, add them all up after reading them, with say sum += temp, while incrementing a count to divide the sum by the count.

so i've worked on things a little more but i still can't get it to print average
here is my code

Code:

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
int main()
{
   char filename[100];
   int tempcount = 0;
   double nextVal;
   double total = 0.0;
   FILE *tempsIn;
   
   tempsIn = fopen("c:\\documents and settings\\christina kestler\\my documents\\temps.txt", "r");
   
   printf("Temperature Analyzer v1.1\n");
   printf("\n");
   printf("What file to analyze?");
   scanf("%lf", "c:\\documents and settings\\christina kestler\\my documents\\temps.txt");
   
   if(tempsIn == NULL ) {
      printf("File could not be opened ... exiting.\n");
      system("pause");
      exit(EXIT_FAILURE);      // quit program
   }
   while(fscanf(tempsIn, "%2.0lf", &nextVal) != EOF) {
      tempcount++;
      total += nextVal;
   }
   
   fclose(tempsIn);
   if (tempcount == 0)
      printf("No values in file.\n");
   else
      printf("Average of %lf values read is %.3lf\n", tempcount, total);
   system("pause");
   return 0;
}

In order to print the average, you must first compute the average.

is it valid to say

Code:

   while(fscanf(tempsIn, "%2.0lf", &nextVal) != EOF)
      tempcount++;
      (total += nextVal) / total;

for computation of the average?

Originally Posted by cakestler

is it valid to say

Code:

   while(fscanf(tempsIn, "%2.0lf", &nextVal) != EOF)
      tempcount++;
      (total += nextVal) / total;

for computation of the average?

No. (Even if you managed to get both statements inside the while loop. Still no.) Presumably division is not such a stranger to you?

no i am not a stranger to division i am a math major, i am a stranger to c programming, i suck i know, but i've reread my book and notes about 10 times now and im still not getting it

Originally Posted by cakestler

no i am not a stranger to division i am a math major, i am a stranger to c programming, i suck i know, but i've reread my book and notes about 10 times now and im still not getting it

So why do you think that "sum / n" (which is what you want) is somehow the same as thing as (sum / sum), if not sum / sum / sum / sum ... / sum (divided n times, once each time through the loop)?

Code:

while(fscanf(tempsIn, "%2.0lf", &nextVal) != EOF) {
      tempcount++;
      total += nextVal;
}

The total already have the total of all the values ( assuming grades ). Since total already have the sum of all the grades then after that you just have to divide the sum of all the grades and divide it to how many grades were retrieved.

ok so i have changed a few things and have my program running and working almost perfectly. i am haveing 2 problems. there are 30 temperatures in my file, yet my program says there are 31, also my average is off by about a .5, i thought that it might have something to do with the count being off, but even computing the average with the incorrect count, the average is still off by a little. here is my code if anyone has any suggestions or hints. thanks

Code:

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

int main()

{
  char inFileName[160];
  int x;
  int tempcount = 0;
  int max = 0;
  int min = 10000;
  double sum = 0;
  FILE *tempsIn;
  
   printf("Temperature Analyzer v1.1\n");
   printf("\n");
   printf("What file to analyze?\n");
   scanf("%s",&inFileName);
  
   tempsIn = fopen("c:\\documents and settings\\christina kestler\\desktop\\temps.txt", "r");
 
   if (inFileName == NULL) {
   printf("File could not be opened.\n");
   system("pause");
   exit(EXIT_FAILURE);    
  }
  
  while(!feof(tempsIn))
  {
    fscanf(tempsIn,"%d",&x);
    tempcount++;
    sum += x;
    
    if(x > max)
    max = x;
    
    if(x < min)
    min = x;
  }
  
  double avg = sum / tempcount;
  
  printf("# of daily temps: %d\n", tempcount);
  printf("Average daily temp: is %0.5lf\n", avg);
  printf("Highest temp: %d\n", max);
  printf("Lowest temp: %d\n", min);
  
  system("PAUSE");	
  return 0;
}

So after you read the last temperature, feof is still false, so your loop won't stop.

do i need a

Code:

fclose(tempsIn);

???
if so that isn't working.