[R] selecting matrix cels by two factors

[Dimitri Joe]

Hi,

I have a (numeric) matrix X of the type

 > X <- matrix(c(1:9),ncol=3,nrow=3)
 > colnames(X) <- c("A","B","C")
 > rownames(X) <- c("D","E","F")

Also, a have a data frame Y like

 > Y <- as.data.frame(cbind(	c("D","E","F","D","E","F"),
+				c("A","C","A","B","B","C") ) )

I want a matrix like

1 4	  		 X["D","A"] X["D","B"]
8 5  or, equivalentely,  X["E","C"] X["E","B"]
3 9			 X["F","A"] X["F","C"]


Any suggestions?
Thanks in advanced,

Dimitri