Standard deviation problem.

[binso]

Hi.
I have written a code to calculate standard deviation. The program runs fine, but it does not give the correct outcome.
For my numberOfentries I used 4 and then 1.0 5.0 -1.4 3.9.

Can anyone spot the problem, I have been looking at it for a while now and can´t figure it out.

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


//void output (double x[] , int staerd);
void read_numbers (double x [] , int staerd);
double deviation (double x[] , int staerd );
double medaltal (double x[] , int staerd);

int main()
{
    int numberOfentries = 0;

    cout << "Enter how many numbers you want to enter: ";
    cin >> numberOfentries;
    const int staerd = numberOfentries;

    double x [staerd];
    read_numbers(x , staerd);
    deviation(x , staerd);
    cout <<"deviation is" << deviation (x , staerd);




    return 0;
}



void read_numbers (double x [], int staerd)
{

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

    for (int i = 0; i < staerd ; i ++ ) // debugger til að sjá hvort tölurnar fóru rétt inn
   { cout << x[i] << " " << endl; }

    return ;
}


double medaltal (double x[] , int staerd)
{
    double sum = 0;
    double medalt = 0;

    for(int i = 0; i < staerd; i++)
    {
        sum += x[i];
    }
    medalt = sum / 4;


    return medalt;

}

/
double deviation (double x[], int staerd )
{
    double deviation;
    double sum2 = 0;
    double medaltal2 = medaltal(x , staerd);

    for ( int i = 0; i < staerd; i++ )
    {
        sum2 += pow((x[i]- medaltal2), 2);
    }
    deviation = sqrt(sum2 / (staerd-1));

return deviation ;

}

[mobotus]

For starters you can't declare your array on line 19 like that the array size must be known at compile time.... unless

You want to do something like

double *x = new double[staerd];

just remember to delete what you made new before exiting your main

delete [] x;

There are a few other things to look at but you should be able to get a good start from here.

[binso]

Hi,
thanks for your reply.
I found out the problem and resolved it.

cin >> numberOfentries;
    const int staerd = numberOfentries;

    double x [staerd];

I am getting the size here from the user.

and there was a number in my deviation calc that was messing up.