C++ Class

[KLane]

I have written the program below to calculate Standard deviation and mean of a given file of data. If I run it gives the wrong answers. Can someone help me go along?

#include <cstdlib>
#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;
class Statistics{
      double x;
      int n;
      double sum;
      double sum2;

      public:

             Statistics(double _x, int n);
             ~Statistics();
             void Accumulate(double data);
             double mean()const;
             double sigma()const;
             void Print() const;

};


int main(){

    double data;

    Statistics a(data, 200);
    a.Print();

    system("PAUSE");
    return EXIT_SUCCESS;
}

Statistics::Statistics(double _x, int n):x(_x),n(n){}

Statistics::~Statistics(){
cout<<"Statistics destructor called"<<endl;
}

void Statistics::Accumulate(double data){//This should add a data item to the accumulated  statistics
     ifstream in("file.txt");
     for(int i=0; i < n ; i++){
     in >> data;
     sum+=data;
     sum2+=data*data;   
     }
     in.close();
     }
double Statistics::mean()const{
     return sum/n;
     }

double Statistics::sigma()const{   
     return sqrt( (sum2 - (sum*mean()))/(n-1));
     }

void Statistics::Print()const{

     cout.precision(8);
     cout << " N     = " << n <<endl; 
     cout << " Mean  = " << mean() <<endl;
     cout << " Sigma = " << sigma()<<endl ;
}

[Clinton Portis]

one thing that i notice is that you got a couple of smiley faces in your code.

[Tsunami49]

Use code brackets, makes it easier to read you code segments. Just put (code) before and (code) after your source code without the space between the 'e' and the ].

#include <cstdlib>
#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;
class Statistics{
double x;
int n;
double sum;
double sum2;

public:

Statistics(double _x, int n);
~Statistics();
void Accumulate(double data);
double mean()const;
double sigma()const;
void Print() const;

};


int main(){

double data;

Statistics a(data, 200);
a.Print();

system("PAUSE");
return EXIT_SUCCESS;
}

Statistics:tatistics(double _x, int n):x(_x),n(n){}

Statistics::~Statistics(){
cout<<"Statistics destructor called"<<endl;
}

void Statistics::Accumulate(double data){//This should add a data item to the accumulated statistics
ifstream in("file.txt");
for(int i=0; i < n ; i++){
in >> data;
sum+=data;
sum2+=data*data;
}
in.close();
}
double Statistics::mean()const{
return sum/n;
}

double Statistics::sigma()const{
return sqrt( (sum2 - (sum*mean()))/(n-1));
}

void Statistics:rint()const{

cout.precision(8);
cout << " N = " << n <<endl;
cout << " Mean = " << mean() <<endl;
cout << " Sigma = " << sigma()<<endl ;
} 

makes it easier to read that's all ;)

[mrnutty]

You don't call Accumulate anywhere. Call it inside your constructor.