Message-ID: <43A34780.4060507@ipea.gov.br>
Date: 2005-12-16T23:02:24Z
From: Dimitri Szerman
Subject: selecting matrix cels by two factors
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