Cumulative standard deviation: Difference between revisions

}</lang>

=={{header|C++}}==

<lang C++>#include <algorithm>

#include <iostream>

#include <iterator>

#include <cmath>

#include <vector>

#include <iterator>

#include <numeric>

double standard_dev( std::vector<double> & ) ;

int main( ) {

double demoset[] = { 2 , 4 , 4 , 4 , 5, 5 , 7 , 9 } ;

int demosize = sizeof demoset / sizeof *demoset ;

std::vector<double> numbers ;

for ( double *d = demoset ; d != demoset + demosize ; ++d )

numbers.push_back( *d ) ;

std::cout << "The standard deviation of\n" ;

std::copy( numbers.begin( ) , numbers.end( ) , std::ostream_iterator<double>( std::cout, " " ) ) ;

std::cout << "\nis " << standard_dev( numbers ) << " !\n" ;

return 0 ;

}

double standard_dev( std::vector<double> & numbers ) {

double mean = std::accumulate( numbers.begin( ) , numbers.end( ) , 0 ) / numbers.size( ) ;

std::vector<double> squares ;

for( std::vector<double>::const_iterator vdi = numbers.begin( ) ; vdi != numbers.end( ) ; vdi++ )

squares.push_back( pow( *vdi - mean , 2 ) ) ;

return pow( std::accumulate( squares.begin( ) , squares.end( ) , 0 ) / squares.size( ) , 0.5 ) ;