Signature Description Parameters
templat<typename T, typename I = unsigned long, typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
struct MADVisitor;
This is a “single action visitor”, meaning it is passed the whole data vector in one call and you must use the single_action_visit() interface.
This functor class calculates 4 different forms of Mean Absolute Deviation. Please see mad_type enum definition above in the type section
          MADVisitor(mad_type mt, bool skip_nan = true)
        
T: Column data type
I: Index type