Hi Carol,
On 07/21/2014 09:10 PM, Richard M. Heiberger wrote:
l = list(c(1,2), c(3,5,6), c(7))
sapply(l, `[`, 1)
Using sapply() works but won't be very efficient if you have a very long
list. If you worry about efficiency, you can do the following (using the
IRanges package from Bioconductor):
> library(IRanges)
> eltlens <- elementLengths(l)
> unlist(l, use.names=FALSE)[cumsum(eltlens) - eltlens + 1L]
[1] 1 3 7
Only worth if the length of your list is > 100000 though...
Cheers,
H.
PS: See http://bioconductor.org/packages/release/bioc/html/IRanges.html
for how to install the IRanges package.
On Mon, Jul 21, 2014 at 3:55 PM, carol white <wht_...@yahoo.com> wrote:
Hi,
If we have a list of vectors of different lengths, how is it possible to
retrieve the first element of the vectors of the list?
l = list(c(1,2), c(3,5,6), c(7))
1,3,7 should be retrieved
Thanks
Carol
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fhcrc.org
Phone: (206) 667-5791
Fax: (206) 667-1319
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
