Signature Description Parameters
#include <DataFrame/DataFrameStatsVisitors.h>

template<typename T,
         typename I = unsigned long,
         typename =
             typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
struct StdVisitor;
        
This functor class calculates the standard deviation of a given column.
    explicit StdVisitor (bool bias = true);
        
See this document and dataframe_tester.cc for examples.
T: Column data type.
I: Index type.