R数据表:左外连接

Question

假设我有两个数据表:

X <- data.table(id = 1:5, L = letters[1:5])

   id L
1:  1 a
2:  2 b
3:  3 c
4:  4 d
5:  5 e

Y <- data.table(id = 3:5, L = c(NA, "g", "h"), N = c(10, NA, 12))

   id  L  N
1:  3 NA 10
2:  4  g NA
3:  5  h 12

有没有可能做一个左外连接X,并Y通过id使用内置的功能的数据表？如果没有,我想构建一个leftOuterJoin具有以下预期输出的函数(例如):

leftOuterJoin(X, Y, on = "id")

   id  L  N
1:  1  a NA
2:  2  b NA
3:  3 NA 10
4:  4  g NA
5:  5  h 12

我试过没有成功:

X[Y, on = "id"]

   id L i.L  N
1:  3 c  NA 10
2:  4 d   g NA
3:  5 e   h 12

我也试过这个,这几乎就是我要找的:

setkey(X, id)
setkey(Y, id)
merge(X, Y, all.x = TRUE)

   id L.x L.y  N
1:  1   a  NA NA
2:  2   b  NA NA
3:  3   c  NA 10
4:  4   d   g NA
5:  5   e   h 12

Answer 1

这是一个更新连接:

library(data.table)
X <- data.table(id = 1:5, L = letters[1:5])
Y <- data.table(id = 3:5, L = c(NA, "g", "h"), N = c(10, NA, 12))
X[Y, on=.(id), c("L", "N"):=.(i.L, i.N)][]
#    id  L  N
# 1:  1  a NA
# 2:  2  b NA
# 3:  3 NA 10
# 4:  4  g NA
# 5:  5  h 12

给你想要的结果.
在这里,我找到了多列的解决方案:

library(data.table)
X <- data.table(id = 1:5, L = letters[1:5])
Y <- data.table(id = 3:5, L = c(NA, "g", "h"), N = c(10, NA, 12))

X[Y, on=.(id), names(Y)[-1]:=mget(paste0("i.", names(Y)[-1]))]

另一个变种:

n <- names(Y)
X[Y, on=.(id), (n):=mget(paste0("i.", n))]