Grouping data topic

Group discrete values.

Functions

group<T, K>(Iterable<T> iterable, K key(T)) → Map<K, List<T>>

Groups the specified iterable of values into an Map from key to list of value.

groupSort<T, K>(Iterable<T> iterable, K key(T), [num valueComparator(List<T>, List<T>) = ascending, num keyComparator(K, K) = ascending]) → List<K>

Groups the specified iterable of elements according to the specified key function, sorts the groups according to the specified valueComparator for values and keyComparator for keys, and then returns a list of keys in sorted order.

index<T, K>(Iterable<T> iterable, K key(T)) → Map<K, List<T>>

Equivalent to group but returns a unique value per compound key instead of an list, throwing if the key is not unique.

rollup<T, R, K>(Iterable<T> iterable, R reduce(List<T>), K key(T)) → Map<K, R>

Groups and reduces the specified iterable of values into an Map from key to value.

rollupSort<T, R, K>(Iterable<T> iterable, R reduce(List<T>), K key(T), [num valueComparator(R, R) = ascending, num keyComparator(K, K) = ascending]) → List<K>

Groups and reduces the specified iterable of elements according to the specified key function, sorts the reduced groups according to the specified valueComparator for values and keyComparator for keys, and then returns a list of keys in sorted order.