Can dplyr join on multiple columns or composite key?

Question

I realize that `dplyr` v3.0 allows you to join on different variables:`left_join(x, y, by = c("a" = "b")` will match `x.a` to `y.b`However, is it possible to join on a combination of variables or do I have to add a composite key beforehand?Something like this:`left_join(x, y, by = c("a c" = "b d")` to match the concatenation of [`x.a` and `x.c`] to [`y.b` and `y.d`]

Answer 1

If you want further reading on this, type ?dplyr::left_join into your console and read the entry for the "by" argument

#join x.a to y.c and x.b to y.d

#it won't concatenate the variables, but it will make sure the combinations of "a b" and "c d" are retained

left_join(x, y, by = c("a" = "c", "b" = "d"))

#here's a coding example

df1 <- tibble(x = 1:4, y = 5:8, z = 9:12)

df2 <- tibble(a = 1:3, b = 5:7, w = 10:12)

left_join(df1, df2, by("x" = "a", "y" = "b"))

The sample code at the end will create a 4x4 tibble with all the data from df1, and corresponding values for w from df2 with NAs for rows that don't have xy matches. if you want, you can still concatenate the columns before or after you join the data.