Array

[1CohAqkS]

Create an array and store the following Student marks 68, 72, 78, 69, 85, 95, 75, 77, 82, 84, 91, 89, 95, 74.

From the following set of marks.
1. Calculate the mean
2. Calculate the standard deviation.

[1CohAqkS]

i have done the coding but there the user is inputting the marks..................im not able to create the array for the marks mentioned above.

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

double deviation(double[] , int);
double mean (double[] , int);
double mean2;

int main ()
{

int size=10;
double x[14];
mean2=0;

cout << "Enter ten numbers:";


for (int i=0; i<14; i++)
{
cin>>x[i];
}

cout << "The mean is:"<<mean(x,14);
cout << endl;
cout << "The standard deviation is:"<<deviation (x,14);
return 0;

}

double mean(double x[], int size)
{
double sum=0;

for ( int i = 0; i <=size; i++ )
{
sum += x[i];
}
mean2=sum/14;
return mean2;
}

double deviation (double x[], int size)
{
double deviation;
double sum2=0;

for ( int i = 0; i <=size; i++ )
{
sum2 += pow((x[i]-mean2),2);
}
deviation= sqrt(sum2/(size-1));
system ("pause");
return deviation;
}

[1CohAqkS]

can any1 help me in doing this.

[1CohAqkS]

plzzzzzzz help meeee plaese........

[z05DSL3A]

Skills wrote:

im not able to create the array for the marks mentioned above.

#include <iostream>

int main()
{
    const int No_of_marks = 14;
    int marks[No_of_marks] = {68, 72, 78, 69, 85, 95, 75, 77, 82, 84, 91, 89, 95, 74};

    for (int i =0; i < No_of_marks; ++i)
    {
        std::cout << "Mark " << i << " = " << marks[i] << std::endl;
    }

    return 0;
}

[1CohAqkS]

now after creating the array how will i b able to code my program?????????????

[z05DSL3A]

#include <iostream>

double mean(int* data_set, int data_count);

int main()
{
    const int No_of_marks = 14;
    int marks[No_of_marks] = {68, 72, 78, 69, 85, 95, 75, 77, 82, 84, 91, 89, 95, 74};

    for (int i =0; i < No_of_marks; ++i)
    {
        std::cout << "Mark " << i << " = " << marks[i] << std::endl;
    }
    std::cout << "The mean is " << mean(marks, No_of_marks) << std::endl;

    return 0;
}

double mean(int* data_set, int data_count)
{
    double value = 0;
    for (int i =0; i < data_count; ++i)
    {
        value += data_set[i];
    }
    value /= data_count;
    return value;
}

You can do the standard deviation

[1CohAqkS]

can any1 help witf standard deviation?????????????????

[Zhuge]

How about trying it yourself first?

[1CohAqkS]

ok mate........

[ne555]

double deviation (double x[], int size)
{
	double deviation;
	double sum2=0;
	
	for ( int i = 0; i <=size; i++ ) //out of bounds
	{
		sum2 += pow((x[i]-mean2),2); //pow is overkill. Also global are evil.
	}
	deviation= sqrt(sum2/(size-1));
	system ("pause"); //why?
	return deviation;
}

What is the problem?

[1CohAqkS]

The problem is that my friend that i dont knw how to put the standard deviation and the mean program given above together to give me answer of mean and standard deviation...............it would be kind enough if u could help me.............................putting it together...........................

[1CohAqkS]

help reh....................

[z05DSL3A]

Your still working on this one? I would strongly suggest that you work through the tutorials
http://www.cplusplus.com/doc/tutorial/

#include <iostream>

double mean(int* data_set, int data_count);
double standard_deviation(int* data_set, int data_count);

int main()
{
    const int No_of_marks = 14;
    int marks[No_of_marks] = {68, 72, 78, 69, 85, 95, 75, 77, 82, 84, 91, 89, 95, 74};

    for (int i = 0; i < No_of_marks; ++i)
    {
        std::cout << "Mark " << i << " = " << marks[i] << std::endl;
    }
    std::cout << "The mean is " << mean(marks, No_of_marks) << std::endl;
    std::cout << "The standard deviation is " << standard_deviation(marks, No_of_marks) << std::endl;

    return 0;
}

double mean(int* data_set, int data_count)
{
    double value = 0;

    for (int i =0; i < data_count; ++i)
    {
        value += data_set[i];
    }
    
    return value / data_count;
}

double standard_deviation(int* data_set, int data_count)
{
    double the_mean = mean(data_set, data_count);
    double num = 0;
    double accumulator  = 0;

    for (int i = 0; i < data_count; ++i)
    {
        num          = (data_set[i] - the_mean);
        accumulator += (num * num);
    }

    return sqrt(accumulator / data_count);
}

[1CohAqkS]

eh blood still cannot compile it yaar.................says sqrt undeclared

[Moschops]

sqrt lives in cmath

http://www.cplusplus.com/reference/clibrary/cmath/

[z05DSL3A]

try adding #include <cmath> then.

[1CohAqkS]

but i only get the answer for mean not for standard deviation.......

[1CohAqkS]

okay i finally got it......no worries and thank you..........

[z05DSL3A]

Judging by past form, you have probably put a system ("pause"); in your code...