collections/window_functions_utils library

Window functions (lag, lead, row_number) over ordered data — roadmap #471.

Functions

lag<T>(List<T> values, int index, int offset) → T?

Lag: value at index i - offset; null if out of range.

lead<T>(List<T> values, int index, int offset) → T?

Lead: value at index i + offset; null if out of range.

rank(List<num> values) → List<int>

Rank: 1-based rank; equal values get same rank, next rank skips.

rowNumber(int index) → int

Row number (1-based index).