data.table (version 1.4.1)

merge: Merge Two Data Tables

Description

Relatively quick merge of data tables based on common keys.

Usage

## S3 method for class 'data.table':
merge(x, y, all = FALSE, all.x = all, all.y = all, ...)

Arguments

x, y

data tables.

all

logical; all = L is shorthand for all.x = L and all.y = L.

all.x

logical; if TRUE, then extra rows will be added to the output, one for each row in x that has no matching row in y. These rows will have 'NA's in those columns that are usually filled w

all.y

logical; analogous to all.x above.

...

Not used at this time.

Value

• A data table based on the merged data tables, sorted by the common keys.

Details

Keys must be in the same order.

See Also

data.table, merge

Examples

(dt1 <- data.table(A = letters[1:10], X = 1:10, key = "A"))
    (dt2 <- data.table(A = letters[5:14], Y = 1:10, key = "A"))
    merge(dt1, dt2)
    merge(dt1, dt2, all = TRUE)

    (dt1 <- data.table(A = letters[rep(1:3, 2)], X = 1:6, key = "A"))
    (dt2 <- data.table(A = letters[rep(2:4, 2)], Y = 6:1, key = "A"))
    merge(dt1, dt2)

    (dt1 <- data.table(A = c(rep(1L, 5), 2L), B = letters[rep(1:3, 2)], X = 1:6, key = "A,B"))
    (dt2 <- data.table(A = c(rep(1L, 5), 2L), B = letters[rep(2:4, 2)], Y = 6:1, key = "A,B"))
    merge(dt1, dt2)