statar (version 0.1.1)

join: Join two data.tables together

Description

Join two data.tables together

Usage

join(x, y, on = intersect(names(x), names(y)), type = "outer",
  suffixes = c(".x", ".y"), check = m ~ m, gen = FALSE, inplace = FALSE,
  update = FALSE)

Arguments

x

The master data.table

y

The using data.table

on

Character vectors specifying variables to match on. Default to common names between x and y.

type

The type of (SQL) join among "outer" (default), "left", "right", "inner", "semi", "anti" and "cross".

suffixes

A character vector of length 2 to apply to overlapping columns. Defaut to ".x" and ".y".

check

A formula checking for the presence of duplicates. Specifying 1~m (resp m~1, 1~1) checks that joined variables uniquely identify observations in x (resp y, both).

gen

Name of new variable to mark result, or the boolean FALSE (default) if no such variable should be created. The variable equals 1 for rows in master only, 2 for rows in using only, 3 for matched rows.

inplace

A boolean. In case "type"= "left" and RHS of check is 1, the merge can be one in-place.

update

A boolean. For common variables in x and y not specified in "on", replace missing observations by the non missing observations in y.

Value

• A data.table that joins rows in master and using datases. Importantly, if x or y are not keyed, the join may change their row orders.

Examples

library(data.table)
x <- data.table(a = rep(1:2, each = 3), b=1:6)
y <- data.table(a = 0:1, bb = 10:11)
join(x, y, type = "outer")
join(x, y, type = "left", gen = "_merge")
join(x, y, type = "right", gen = "_merge")
join(x, y, type = "inner", check = m~1)
join(x, y, type = "semi")
join(x, y, type = "anti")
setnames(y, "bb", "b")
join(x, y, on = "a")
join(x, y, on = "a", suffixes = c("",".i"))
y <- data.table(a = 0:1, bb = 10:11)
join(x, y, type = "left", check = m~1, inplace = TRUE)
x <- data.table(a = c(1,2), b=c(NA, 2))
y <- data.table(a = c(1,2), b = 10:11)
join(x, y, type = "left", on = "a",  update = TRUE)
join(x, y, type = "left", on = "a", chec = m~1, inplace = TRUE,  update = TRUE)