// C++11 version
// Computes average and standard deviation 
// for data stored in std::vector 
#include <vector>
#include <cmath>

void get_stats(const std::vector<double> & x, double & average, double & sigma )
{
  // average = sum_i=1^N x_i /N
  //
  //              sum_i=1^N (x_i-<x>)^2  
  // sigma = sqrt( -------------------- )
  //                    N-1              
  int N = x.size();  
  average=0; sigma = 0;    
  for (auto x_i: x) {average += x_i;}
  average /= N;
  for (auto x_i: x) {sigma += pow(x_i-average,2);}
  sigma = sqrt(sigma/(N-1));
}