columns_used

generic additional arguments (not used)

character, if not NULL set of columns used from above.

using

logical, if TRUE perform unused value elimination.

contract

A query generator based on Edgar F. Codd's relational
algebra and operator names (plus experience using 'SQL' at big data
scale).  The design represents an attempt to make 'SQL' more teachable by
denoting composition a sequential pipeline notation instead of nested
queries or functions.  Package features include: data processing trees
or pipelines as observable objects (able to report both columns
produced and columns used), optimized 'SQL' generation as an explicit
user visible modeling step, and convenience methods for applying query
trees to in-memory data.frames.

columns_used: Return columns used

Description

Usage

Arguments

Value