data.table (version 1.7.7)
Extension of data.frame for fast indexing, fast ordered joins,
fast assignment, fast grouping and list columns.
Description
Enhanced data.frame. Fast indexing, fast ordered joins, fast assignment, fast grouping and list columns in a short and flexible syntax. i and j may be expressions of column names directly, for faster development. Example: X[Y] is a fast join for large data.