Function to average array

[JHus00]

#include <cstdlib>
#include <iostream>
#include <fstream>
using namespace std;

double average(int sum, int numElms)
{
	int i;
	double avg;

    avg = sum/numElms;


	return sum;
}

int main()
{
	ifstream fileIn;
    const int MAX_ARRAY = 500;
    int scores[MAX_ARRAY];
    int numElms, sum;
    int i;

    fileIn.open("pgm5data.txt"); //open file

    if (fileIn.fail() )
    {
        cout << "Error opening file";
        exit(-1);
    }

    i = 0;
    fileIn >> scores[i];
    while (!fileIn.eof() && i < MAX_ARRAY)
    {
        i++;
        fileIn >> scores[i];
		sum+=scores[i];
    }
    numElms = i;

	cout << "\nSum is: " << average(sum, numElms);

    return 0;
}

I don't understand why im getting huge numbers that aren't anywhere close to what I need. Advice? thanks!

[MyrtleTurtle]

Maybe your function should return avg instead of sum?

[JHus00]

Your right, but Im still gettting the same error

[MyrtleTurtle]

Hmm...

try initializing sum to 0, see if that helps.

int numElms, sum=0;

//instead of 
int numElms, sum;

[JHus00]

Same thing :(

[JHus00]

I GOT IT, Line 34 should not be there.

[JHus00]

Nevermind its giving me a different number for each average

[MyrtleTurtle]

After compiling your code using my own input file I see the problem. You were adding the sum in the wrong place, which was after the last (unsuccessful) read from the file. It was adding a way huge number at the end, which made your calculations off.

I put a couple extra cout's in there to test. Remove them and this code should be what you want:

i = 0;
    fileIn >> scores[i];
    cout<<"scores[i]: "<<scores[i]<<endl;
    while (!fileIn.eof() && i < MAX_ARRAY)
    {
        sum+=scores[i];
        cout<<endl<<i<<": "<<sum<<endl;
        i++;
        fileIn >> scores[i];
        cout<<"scores[i]: "<<scores[i]<<endl;
			
    }
    numElms = i;

	cout << "\nAvg is: " << average(sum, numElms);

[JHus00]

Thanks alot!

[jonsca]

Beware of this in your function:

double average(int sum, int numElms)
{
	//int i;
	double avg;
        avg = sum/numElms;
	return avg;
}

Since the two operands are integers the result placed into avg will be an integer result (so truncated or 0 if the denominator is bigger) despite the fact that it's a double variable. Cast one (or both) of the operands to a double to get the correct answer. avg = ((double) sum)/numElms;

[MyrtleTurtle]

It was adding a way huge number at the end, which made your calculations off.

Since I cannot edit the post, I'll just add another reply here.

I think the reason for the way huge number is because your array is un-initialized. In case anyone (who didn't know already) wants to know. :)

[jonsca]

Since I cannot edit the post, I'll just add another reply here.

I think the reason for the way huge number is because your array is un-initialized. In case anyone (who didn't know already) wants to know. :)

I wasn't undermining what you wrote at all. Sorry if I wasn't clear about that. I was just warning against another issue that was going to manifest itself one way or the other.