From: Gabor Grothendieck <ggrothendieck_at_gmail.com>

Date: Tue 17 May 2005 - 11:28:01 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue May 17 11:33:25 2005

Date: Tue 17 May 2005 - 11:28:01 EST

On 5/16/05, Luke <jyzz88@gmail.com> wrote:

> 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)
**> >
*

>

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue May 17 11:33:25 2005

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