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

From: Luke <jyzz88_at_gmail.com>
Date: Tue 17 May 2005 - 11:23:37 EST

Yes, it works. Althought I can understand the help page of sapply, I don't know why it works. What is "["?

-Luke

On 5/16/05, Gabor Grothendieck <ggrothendieck@gmail.com> wrote:
> 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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