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questionsolved Working with 2D arrays

mattzorx (21)
I am working on a project using 2D arrays to display a class's individual grades, averages, and a class average. I am able to display the grades and class average, but my STUDENT AVERAGE Letter Grade is returning a number, when I thought my if else ladder was telling it to return the Char. Any help would be much appreciated.

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#include <iostream>
#include <iomanip>
using namespace std;

//file level scope
const int columns = 4;
const int nColumns = 20;

//prototype for 2d array
void showNamesAndScores(int scores[][columns], char names[][nColumns], int);

//calcAvg
double calcAvg(int X[][columns], int);

//studentAvg
char studentAvg(int X[][columns], int);

int main()
{
	//declare rows & columns
	const int rows = 5;
	
	//declare 2d array
	int scores[rows][columns];
	char names[rows][nColumns];
	
	//populate 2d array
	for(int i=0; i<rows ;i++)
	{
		cout<<"Enter Name of student"<<i+1<<": ";
		cin>>names[i];
		cout<<endl;
	}
	for(int i=0; i<rows; i++)
	{
		cout<<"Enter "<<columns<<" scores for row "<<i+1<<": ";
		for (int j=0; j<columns; j++)
		{
			cin>>scores[i][j];
		}
	}
	
	
	//display scores with function
	showNamesAndScores(scores, names, rows);
	
	//display avg
	double avg = calcAvg(scores, rows);
	cout<<"Avg: "<<avg<<endl;
	
	
	//display LetterGrade
	double sAvg = studentAvg(scores, avg);
	cout<<"Letter Grade: "<<sAvg<<endl;
	
	
}//endmain



//defines a function to accept 2d array


void showNamesAndScores(int scores[][columns], char names[][nColumns], int rows)
{
	for(int i=0; i<rows; i++)
	{
		cout<<names[i];
		cout<<setw(15);
		for(int j=0; j<columns; j++)
		{
			cout<<scores[i][j]<<" ";
			
		}
		cout<<endl;
		
		
	}
	
}//end names and scores

//calcAvg
double calcAvg(int X[][columns], int s)
{
	double a;
	
	double sum = 0;
	for(int i=0; i<s; i++)
	{
		for(int j=0; j<columns; j++)
		{
			sum += X[i][j];
		}
	}
	
	a = sum/(s*columns);
	
	return a;
	
}//endcalcAvg


//studentAvg
char studentAvg(int scores[][columns], int rows)
{
	double avg;
	int sum = 0;
	char grade;
	for(int i=0; i<rows; i++)
	{
		sum += scores[i][columns];
		
	}
	avg = sum/rows;
	
	if(avg >= 90)
		grade = 'A';
	else if(avg >= 80 && avg < 90)
		grade = 'B';
	else if(avg >= 70 && avg < 80)
		grade = 'C';
	else if(avg >= 60 && avg < 70)
		grade = 'D';
	else
		grade = 'F';
	
	return grade;
	
}//endstudentAvg
Last edited on
mbittel12 (21)
I believe it is something very simple that I am also overlooking. In the bottom of your function studentAvg could you put in a cout << grade to see what it does and let me know.
mattzorx (21)
apparently these kids ace their tests. i input 100s for all grades. should be an A where that F is right?

[Session started at 2009-11-02 22:20:14 -0600.]
Enter Name of student1: bob

Enter Name of student2: tim

Enter Name of student3: john

Enter Name of student4: matt

Enter Name of student5: alice

Enter 4 scores for row 1: 100 100 100 100
Enter 4 scores for row 2: 100 100 100 100
Enter 4 scores for row 3: 100 100 100 100
Enter 4 scores for row 4: 100 100 100 100
Enter 4 scores for row 5: 100 100 100 100
bob            100 100 100 100 
tim            100 100 100 100 
john            100 100 100 100 
matt            100 100 100 100 
alice            100 100 100 100 
Avg: 100
F  Letter Grade: 70

The Debugger has exited with status 0.
mattzorx (21)
UPDATE:

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#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

//file level scope
const int columns = 4;
const int nColumns = 20;

//prototype for 2d array
void showNamesAndScores(int scores[][columns], char names[][nColumns], int);

//calcAvg
double calcAvg(int X[][columns], int);

//studentAvg
char studentAvg(int X[][columns], int);

//deviation
void deviation(int X[][columns], double Y[][columns], int, double);

//variance
void variance(double Y[][columns],int);

int main()
{
	//declare rows & columns
	const int rows = 5;
	
	//declare 2d array
	int scores[rows][columns];
	char names[rows][nColumns];
	
	//populate 2d array
	for(int i=0; i<rows ;i++)
	{
		cout<<"Enter Name of student"<<i+1<<": ";
		cin>>names[i];
		cout<<endl;
	}
	for(int i=0; i<rows; i++)
	{
		cout<<"Enter "<<columns<<" scores for row "<<i+1<<": ";
		for (int j=0; j<columns; j++)
		{
			cin>>scores[i][j];
		}
		cout<<endl;
	}
	
	
	//display scores with function
	showNamesAndScores(scores, names, rows);
	
	//display avg
	double avg = calcAvg(scores, rows);
	deviation(scores, devi, rows, avg);                                     //error: 'devi' not declared in this scope.   ???
	cout<<"Class Avg: "<<avg<<endl;
	variance(devi,rows);                                                         //error: 'devi' not declared in this scope.   ???
	
	
}//endmain



//defines a function to accept 2d array


void showNamesAndScores(int scores[][columns], char names[][nColumns], int rows)
{
	for(int i=0; i<rows; i++)
	{
		cout<<names[i];
		cout<<setw(15);
		for(int j=0; j<columns; j++)
		{
			cout<<scores[i][j]<<" ";
			
		}
		cout<<endl;
		
		
	}
	
}//end names and scores

//calcAvg
double calcAvg(int X[][columns], int s)
{
	double a;
	
	double sum = 0;
	for(int i=0; i<s; i++)
	{
		for(int j=0; j<columns; j++)
		{
			sum += X[i][j];
		}
	}
	
	a = sum/(s*columns);
	
	return a;
	
}//endcalcAvg


//studentAvg
char studentAvg(int scores[][columns], int rows)
{
	int sum = 0;
	char grade;
	for(int j=0; j<columns; j++)
	{
		sum += scores[rows][j];
		
	}
	double avg = sum/rows;
	cout<<"avg"<<avg;
	
	if(avg >= 90)
		grade = 'A';
	else if(avg >= 80 && avg < 90)
		grade = 'B';
	else if(avg >= 70 && avg < 80)
		grade = 'C';
	else if(avg >= 60 && avg < 70)
		grade = 'D';
	else
		grade = 'F';
	
	cout<<"Letter Grade: ";
	return grade;
	
}//endstudentAvg

//calcDeviation
void deviation(int scores[][columns],double devi[][columns], int rows, double avg)
{
	for(int i=0; i<rows; i++)
	{
		for(int j=0; j<columns; j++)
		{
			devi[i][j] = scores[i][j] - avg;
		}
		
	}
	
	
}//endDeviation

//calcVariance
void variance(double devi[][columns], int rows)
{
	double v = 0;
	for(int i=0; i<rows; i++)
	{
		for(int j=0; j<columns; j++)
		{
			v += pow(devi[i][j], 2);
		}
	}
	
	v= v/rows;
	
	cout<<"Variance: "<<v<<endl;
	
}//endVariance
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