[R] Index list by other list (w/ logical elements)?

[Marianne Promberger]

I have two lists of the same shape, like this:

x <- list()
x[[1]] <- c("one","two")
x[[2]] <- c("three","four","five")

y <- list()
y[[1]] <- c(TRUE,FALSE)
y[[2]] <- c(FALSE,TRUE,TRUE)

I would like to index x "by" y, that is, the result in this case
should be:

 z
[[1]]
[1] "one"

[[2]]
[1] "four"  "five"


I was hoping 
sapply(x,"[",y) 
would work, but it doesn't.

I guess I need to sapply twice, like 
sapply(x, function() { sapply(y ... 
but I can't figure it out.

Many thanks for any pointers

Marianne


-- 
Marianne Promberger PhD, King's College London
http://promberger.info
R version 2.11.1 (2010-05-31)
Ubuntu 9.04