dplyr (version 0.3)

join: Join two tbls together.

Description

These are generic functions that dispatch to individual tbl methods - see the method documentation for details of individual data sources. x and y should usually be from the same data source, but if copy is TRUE, y will automatically be copied to the same source as x - this may be an expensive operation.

Usage

inner_join(x, y, by = NULL, copy = FALSE, ...)
left_join(x, y, by = NULL, copy = FALSE, ...)
semi_join(x, y, by = NULL, copy = FALSE, ...)
anti_join(x, y, by = NULL, copy = FALSE, ...)

Arguments

x,y

tbls to join

by

a character vector of variables to join by. If NULL, the default, join will do a natural join, using all variables with common names across the two tables. A message lists the variables so that you can check they're right.

To join by different variables on x and y use a named vector. For example, by = c("a" = "b") will match x.a to y.b.

copy

If x and y are not from the same data source, and copy is TRUE, then y will be copied into the same src as x. This allows you to join tables across srcs, but it is a potentially expensive operation so you must opt into it.

...

other parameters passed onto methods

Join types

Currently dplyr supports four join types:

inner_join

return all rows from x where there are matching values in y, and all columns from x and y. If there are multiple matches between x and y, all combination of the matches are returned.

left_join

return all rows from x, and all columns from x and y. If there are multiple matches between x and y, all combination of the matches are returned.

semi_join

return all rows from x where there are matching values in y, keeping just columns from x.

A semi join differs from an inner join because an inner join will return one row of x for each matching row of y, where a semi join will never duplicate rows of x.

anti_join

return all rows from x where there are not matching values in y, keeping just columns from x

Grouping

Groups are ignored for the purpose of joining, but the result preserves the grouping of x.