小编FOM*_*OMH的帖子

加入数据表:

X <- data.table(A = 1:4, B = c(1,1,1,1)) 
#    A B
# 1: 1 1
# 2: 2 1
# 3: 3 1
# 4: 4 1

Y <- data.table(A = 4)
#    A
# 1: 4

通过

X[Y, on = .(A == A)]
#    A B
# 1: 4 1

返回预期结果.但是,我希望这条线:

X[Y, on = .(A < A)]
#    A B
# 1: 4 1
# 2: 4 1
# 3: 4 1

回来

   A B
1: 1 1 …