Removing one table from another in R [closed]

Answer 1

library(data.table)
A = data.table(Col1 = 1:4, Col2 = 4:1, Col3 = letters[1:4])
#   Col1 Col2 Col3
#1:    1    4    a
#2:    2    3    b
#3:    3    2    c
#4:    4    1    d

B = data.table(Col1 = c(1,3,5), Col2 = c(4,2,1))
#   Col1 Col2
#1:    1    4
#2:    3    2
#3:    5    1

A[!B, on = c("Col1", "Col2")]
#   Col1 Col2 Col3
#1:    2    3    b
#2:    4    1    d