Grader [Standard Deviation, Mean, Categorizing]

[nvc5221]

I am a beginner to C++ and I am having some issues with my output of my code. Here is the question.

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Project objective: write a program that takes a list of final scores for a class and determines: 1) the mean (Greek letter mu), 2) the standard deviation (Greek letter sigma), and 3) the number of grades in each category (A, A-, B+, B-, C+, C, C-, D+, D, and F).
Prompt the user for the name of a file containing the final scores, up to 100 scores, such as (without the commas):
100, 94, 59, 83, 57, 11, 92, 76, 37, 89, 74, 59, 65, 79, 49, 89, 89, 75, 64, 82, 15, 74, 82, 68, 92, 61, 33, 95, 91, 82, 89, 64, 43, 93, 86, 65, 72, 40, 42, 90, 81, 62, 90, 89, 35, 81, 48, 33, 94, 81, 76, 86, 67, 70, 100, 80, 83, 78, 96, 58
Note: m = 71.47 s = 20.98

Determine the maximum score, the minimum score, the range of scores (maximum – minimum) and a table with column headings:

Grade
Number of scores

using the following scoring (where m is the mean, s is the standard deviation, and x is an individual score):

A : m+ 4/3 s <= x
A– : m+ 3/3 s <= x < m+ 4/3 s
B+ : m+ 2/3 s <= x < m+ 3/3 s
B : m+ 1/3 s <= x < m+ 2/3 s
B– : m+ 0/3 s <= x < m+ 1/3 s
C+ : m– 1/3 s <= x < m+ 0/3 s
C : m– 2/3 s <= x < m– 1/3 s
C– : m– 3/3 s <= x < m– 2/3 s
D+ : m– 4/3 s <= x < m– 3/3 s
D : m– 5/3 s <= x < m– 4/3 s
F : x < m– 5/3 s
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#include <iostream>
#include <cmath>
#include <fstream>
#include <iomanip>
using namespace std;

float deviation(float sum, float mean, float N);
float mean(float vector[], int size);
float sum(float vector[], int size);

int main()
{
	ifstream inFile;
	float N;
	int size = 0;
	const int Numlist = 1000;
	float totalSum;
	float avg = 0.0;
	int max = 100;
	int min = 11;
	double m = 71.47;
	double s = 20.98;

	double List[Numlist];

	inFile.open("input.txt");
	if (inFile.fail())
	{
		cout << "Error: could not open input.txt" << endl;
		exit(EXIT_FAILURE);
	}

	for (int count = 0; count < Numlist; ++count){
		inFile >> List[count];
		if (!inFile)break;
	}

	float standard_deviation[100];
	inFile >> N;
	while ((!inFile.eof()) && (size<Numlist))
	{
		standard_deviation[size] = N;
		size++;
		inFile >> N;
	}

	totalSum = sum(standard_deviation, size);
	avg = mean(standard_deviation, size);

	cout << "Standard Deviation = " << deviation(totalSum, avg, size) << endl;
	cout << "Mean = " << mean(avg) << endl;
	cout << "Maximum Score = " << max << endl;
	cout << "Minimum Score = " << min << endl;
	cout << "Range = " << (max - min) << endl;
	cout << "Grade" << "\t" << "Number of Scores" << "\t" << endl;

	system("pause");
	return 0;
}
//-----------------------------
//Sum Function
//-----------------------------

float sum(float vector[], int size)
{
	float theSum;
	theSum = 0.0;
	for (int N = 0; N < size; N++)
	{
		theSum += vector[N];
	}

	return theSum;
}
//-----------------------------
//Mean Function
//-----------------------------

float mean(float vector[], int size)
{
	float sum = 0.0, mean = 0.0;

	for (int i = 0; i < size; i++)
	{
		mean += vector[size];
	}

	if (size == 0)
		mean = 0.0;
	else
		mean = mean / size;

	return mean;
}

//-----------------------------
//Deviation function
//-----------------------------

float deviation(float sum, float mean, float N)
{
	double S;
	double U;

	U = (pow(sum - mean, 2));
	S = (sqrt(U / N));

	return S;
}

I believe my issue is in the Mean function, I am getting an error for (avg) at line 51:
cout << "Mean = " << mean(avg) << endl;
"Error: argument of type "float" is incompatible with parameter of type "float*"
I cant seem to find the issue.

I am also having issues trying to understand how to format the table, and how to categorize the individual grades into the correct letter grades.

[newbiee999]

On line 51, you are passing a float variable into the mean() function.
The problem is that your mean function is defined to have two parameters: a float vector and an int variable. So instead of passing a vector and an integer, you are passing a float variable 'avg' into the function and that's why you're getting the error.
You need to either redefine the function prototype or pass in proper arguments into the function.

Now I'm not sure if I understand your second concern properly.
So to categorize number grades into letter grades, you can use if else statement or switch statements to do it.
For example, for the first 'A : m+ 4/3 s <= x'

char letterGrade = 'z'; // initialize it to a char
if ( (mean + (4/3)*standard_deviation) <= score)
{
   letterGrade = 'A';
}
else if ... // same thing for other conditions 

Hope that helps!

[nvc5221]

Thanks man! That really helps, but which arguments would I need to change to pass proper arguments into the function?