Subsetting a data frame to the rows not appearing in another data frame

Question

I have a data frame A with observations

    Var1   Var2  Var3
     1       3    4
     2       5    6
     4       5    7
     4       5    8
     6       7    9         


        

Answer 1

dplyr has a nice anti_join function that does exactly that:

> library(dplyr)
> anti_join(A, B)
Joining by: c("Var1", "Var2", "Var3")
  Var1 Var2 Var3
1    6    7    9
2    4    5    8
3    4    5    7