Hi,
assuming you know the indexes of names:
seq <- 1:100 ; l <- vector("list", 100) ; for (i in seq) {l[[i]] <-
list(species=seq[i], name=as.character(seq[i])) }
unlist(l)[seq(2, 200, 2)] #or,
as.character(unlist(l)[seq(2, 200, 2)])
> Date: Tue, 13 Aug 2013 12:39:58 +0000
> From: "Novack-Gottshall, Philip M." <pnovack-gottsh...@ben.edu>
> To: "r-sig-ecology@r-project.org" <r-sig-ecology@r-project.org>
> Subject: [R-sig-eco] Extracting list elements
> Message-ID:
> <8cf6fe2c677ea94f94fa6285289bae68088ea...@benmail01.ben.pri>
> Content-Type: text/plain
>
> All,
>
> Please excuse what may be a slightly off-topic question. I'm having trouble
> extracting elements from a list of lists.
>
> Here is an example:
>
> # Make list of lists:
>
> seq <- 1:100
>
> l <- vector("list", 100)
>
> for (i in seq) {l[[i]] <- list(species=seq[i], name=as.character(seq[i])) }
>
>
>
> # Extract second elements:
>
> l$name # NULL
>
> l[seq]$name # also NULL
>
> s <- unlist(lapply(seq, function(seq) l[[seq]]$name))
>
>
>
> The lapply() call works fine, but it seems quite inefficient or indirect. Can
> anyone suggest a more intuitive extraction?
>
> Thanks,
> Phil
>
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Phil Novack-Gottshall
> Assistant Professor
> Department of Biological Sciences
> Benedictine University
> 5700 College Road
> Lisle, IL 60532
>
> pnovack-gottsh...@ben.edu<mailto:pnovack-gottsh...@ben.edu>
> Phone: 630-829-6514
> Fax: 630-829-6547
> Office: 332 Birck Hall
> Lab: 107 Birck Hall
> http://www1.ben.edu/faculty/pnovack-gottshall
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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