dplyr (version 0.4.3)

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, ...)
right_join(x, y, by = NULL, copy = FALSE, ...)
full_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 x, 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. Rows in x with no match in y will have NA values in the new columns. If there are multiple matches between x and y, all combinations of the matches are returned.

right_join

return all rows from y, and all columns from x and y. Rows in y with no match in x will have NA values in the new columns. If there are multiple matches between x and y, all combinations 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.

full_join

return all rows and all columns from both x and y. Where there are not matching values, returns NA for the one missing.

Grouping

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