Re: [R] how to use list index to get vector

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Tue 17 May 2005 - 10:56:31 EST

On 5/16/05, Luke <jyzz88@gmail.com> wrote:
> I have a simple question, but I couldn't find the answer in R manuals.
>
> Assume I have a list:
> > foo <- list()
> > foo[[1]] <- c(1, 2, 3)
> > foo[[2]] <- c(11,22,33)
> > foo[[3]] <- c(111,222,333)
> > foo
> [[1]]
> [1] 1 2 3
>
> [[2]]
> [1] 11 22 33
>
> [[3]]
> [1] 111 222 333
>
> How to use list index to get a vector of, say, the first elements of
> list elements?
> That is, how to get a vector c(1, 11, 111) from foo?
>
> foo[[]][1] doesn't work.
>

Try this:

sapply(foo, "[", 1)



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