tables::ftable::agg
template <is_table T,is_tuple_unique Gs>
template<typename... Ss,typename... Fs>
requires (
(sizeof...(Ss) == sizeof...(Fs))
&& ( all_in<std::tuple<Ss...>,tuple_ext::remove_t<Gs,typename T::ts_t>> )
&& ( is_col_to_prim_f<Fs,typename T::p_of_t<Ss>> && ... )
)
auto
ftable<T,Gs>::agg(const Fs... fs) constApplies aggregate function to groups.
Example
Code
#include <cpptables/table.hh>
#include <iostream>
using namespace tables;
using namespace std;
struct col0 { constexpr static char const * const name = "col0"; };
struct col1 { constexpr static char const * const name = "col1"; };
struct col2 { constexpr static char const * const name = "col2"; };
using table_t = table<
pair<col0,string_view>,
pair<col1,unsigned>,
pair<col2,double>
>;
void fby_agg()
{
const table_t t(
{"A", "B", "C", "A", "B", "C", "A", "B", "C"},
{1,10,100,2,20,200,3,30,300},
{100.0,200.0,300.0,400.0,500.0,600.0,700.0,800.0,900.0}
);
const auto fsum = [](const column<auto>& xs) { return xs.sum(); };
const auto t1 = t.fby<col0>().agg<col1>(fsum);
cout << t1 << "\n";
const auto favg = [](const column<auto>& xs) { return xs.avg(); };
const auto t2 = t.fby<col0>().agg<col1,col2>(fsum,favg);
cout << t2 << "\n";
}