Signature Description

enum class mad_type : unsigned char  {
    mean_abs_dev_around_mean = 1,     // Mean of absolute distances from mean
    mean_abs_dev_around_median = 2,   // Mean of absolute distances from median
    median_abs_dev_around_mean = 3,   // Median of absolute distances from mean
    median_abs_dev_around_median = 4, // Median of absolute distances from median
};
      
This defines different ways of calculating averages around averages, in other words different types of Mean Absolute Deviation.

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

template<typename T, typename I = unsigned long>
struct MADVisitor;

// -------------------------------------

template<typename T, typename I = unsigned long>
using mad_v = MADVisitor<T, I>;
        
This is a “single action visitor”, meaning it is passed the whole data vector in one call and you must use the single_act_visit() interface.

This functor class calculates 4 different forms of Mean Absolute Deviation. Please see mad_type enum definition above in the type section
    explicit
    MADVisitor(mad_type mt, bool skip_nan = true)
        
T: Column data type
I: Index type
static void test_MADVisitor()  {

    std::cout << "\nTesting MADVisitor{ } ..." << std::endl;

    std::vector<unsigned long>  idx =
        { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
          21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 };
    std::vector<double> d1 =
        { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
          21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 };
    MyDataFrame         df;

    df.load_data(std::move(idx), std::make_pair("col_1", d1));

    MADVisitor<double>  mad_visitor1(mad_type::mean_abs_dev_around_mean);
    const auto          result1 = df.single_act_visit<double>("col_1", mad_visitor1).get_result();

    assert(result1 == 10.0);

    MADVisitor<double>  mad_visitor2(mad_type::mean_abs_dev_around_median);
    const auto          result2 = df.single_act_visit<double>("col_1", mad_visitor2).get_result();

    assert(result2 == 10.0);

    MADVisitor<double>  mad_visitor3(mad_type::median_abs_dev_around_mean);
    const auto          result3 = df.single_act_visit<double>("col_1", mad_visitor3).get_result();

    assert(result3 == 5.25);

    MADVisitor<double>  mad_visitor4(mad_type::median_abs_dev_around_median);
    const auto          result4 = df.single_act_visit<double>("col_1", mad_visitor4).get_result();

    assert(result4 == 5.25);
}