Calculate Average by dividing with unknown number in array

[wittykitty]

I have viewed a lot of threads out there relating to what I am looking for and can't seem to find one that will help. I am reading data in from a file. Even though I already know how many names are stored in the file, I need to write this program to average from an unknown number in the data file. The entire program works except for my float getAverageGrade function. I have tried everything and it will only print out -NaN. Any help is greatly appreciated!!!

#include <iostream>
#include <string>
#include <fstream>
#include <iomanip>

using namespace std;

void getLetterGrade(float grade[], char lettergrade[], int count);
float getAverageGrade (float grade[], int count);
void printResult (float grade[], string name[], char lettergrade[], int count, \
float average);

int main ()

{
  float average;
  char lettergrade[50];
  string name[50];
  float grades[50];
  int count=0;

  ifstream fp;
  fp.open ("grades2.dat");

  if (!fp)
    {
      cout<<"Error\n";
      return 0;
    }
  while (fp.eof() == false)

    {
      fp>>name[count];
      fp>>grades [count];
      count++;
    }
      getLetterGrade(grades, lettergrade, count);
      getAverageGrade (grades, count);
      printResult (grades, name, lettergrade, count, average);

fp.close();

  return 0;

}

void getLetterGrade (float grades[], char lettergrade[], int count)

{

  for (int i=0; i<count; i++)
    {
      if (grades[i]>=90)
        lettergrade[i]='A';
      else if (grades[i]>=80)
        lettergrade[i]='B';
      else if (grades[i]>=70)
        lettergrade[i]='C';
      else if (grades[i]>=60)
        lettergrade[i]='D';
      else
        lettergrade[i]='F';
    }
}

float getAverageGrade (float grades[], int count)
{
  float sum;
  float average;

  for (int i=0; i<count; i++)
    {
      sum += grades[i];
    }

  average=sum/i; //I have tried this in the loop and in a separate loop and I am having no success!
}

void printResult (float grades[], string name[], char lettergrade[], int count,\
 float average)

{
  for (int i=0; i<count; i++)
}

[jonsca]

i goes out of scope (disappears) after your for loop has finished. Divide by count instead

[Dave Sinkula]

Or change the scope of i . Remember to return a value. And to initialize sum.

float getAverageGrade (float grades[], int count)
{
  float sum = 0;
  float average;
  int i;
  for (i=0; i<count; i++)
    {
      sum += grades[i];
    }

  average=sum/i; //I have tried this in the loop and in a separate loop and I am having no success!
  return average;
}

Regarding...

while (fp.eof() == false)

Avoid Loop Control Using eof()

[jonsca]

Thanks DS, I totally glossed over it...

[wittykitty]

Or change the scope of i . Remember to return a value. And to initialize sum.

float getAverageGrade (float grades[], int count)
{
  float sum = 0;
  float average;
  int i;
  for (i=0; i<count; i++)
    {
      sum += grades[i];
    }

  average=sum/i; //I have tried this in the loop and in a separate loop and I am having no success!
  return average;
}

Regarding...

while (fp.eof() == false)

Avoid Loop Control Using eof()

.

[wittykitty]

I initialized sum (sorry that was a beginners error :-() And I am dividing by count, and added the return average, however, I am still getting the -NaN value for average. Argh

[jonsca]

Do you have: average = getAverageGrade(grades, count); back in main()?
(you are trying to send it into your output function but if you haven't returned it to main properly from the getAvgGrade then it will contain garbage)

[wittykitty]

THANKS!!!! That was the kicker! Sorry, I just started learning this 3 months ago so I am bound to make these kind of errors. I really appreciate your help!!!

[jonsca]

No prob at all :) Good luck with it.