add_cols: Adds cols from data.table SOURCE to data.table TARGET

In matthiaskaeding/matthiastools: Collection of helper functions

Description

Only done when there if rows are uniquely identified by on Returns TARGET invisibly

Usage

add_cols(TARGET, SOURCE, on, cols)

Arguments

TARGET	Target data.table
SOURCE	Source data.table
on	Which variables to join on. When unequal for TARGET and SOURCE, must be named vector, where the names correspond to the SOURCE.
cols	Which cols to add

Examples

TARGET = data.table(id = rep(1:10, each = 3))
SOURCE = data.table(id = 1:5)[, x := rnorm(.N)][, y := rnorm(.N)]
add_cols(TARGET, SOURCE, on = "id", cols = c("x", "y"))
TARGET[]
# Case of unequal named join vars
X = data.table(id0 = 1:10)
Y = data.table(id1 = 3:5)[, z := c("a", "b", "c")]
add_cols(X, Y, on = c("id1" = "id0"), cols = "z")
X[]

matthiaskaeding/matthiastools documentation built on Feb. 22, 2022, 5:09 p.m.