R help - Feb 2014 - Exclude lines in based in multiple strings

Hi, 
Try: 
##Assuming X and Y are matrices (as stated) 
Y[!Y %in% X,,drop=FALSE] 
# ? ? numberall 
#[1,] "gen3" ? 
#[2,] "gen4" ? 
#[3,] "genx4" ? 
A.K. 


I would like to exclude entire lines in matrix "Y" based in 2 collumns
in matrix "X":

Matrix "X": 

? number1 ?number2 
? ?gen1 ? ? genx1 ? 
? ?gen1 ? ? genx2 
? ?gen2 ? ? genx3 
? ?gen2 ? ? genx5 

Matrix "Y": 

? ?numberall 
? ? gen1 
? ? genx1 
? ? gen2 
? ? genx2 
? ? gen3 
? ? genx3 
? ? gen4 
? ? genx4 

Expected output matrix 

? ?numberall 
? ? gen3 
? ? gen4 
? ? gen4x 

Cheers.