Here are a few possibilities. The first three use seq_along and the last two use if and length:
x[ !seq_along(x) %in% a[s] ] x[ !match(seq_along(x), a[s], 0) ] x[ setdiff(seq_along(x), a[s]) ] if (length(a[s])) x[-a[s]] else x x[ if (length(a[s])) -a[s] else TRUE ] On Thu, Jun 5, 2008 at 3:16 PM, roger koenker <[EMAIL PROTECTED]> wrote: > Negative indexing is often handy, but I'm in need of an appropriate idiom > for handling cases in which the index set can be null: > > x <- rnorm(5) > a <- 1:5 > s <- rep(FALSE,5) > y <- x[-a[s]] > > # I'd like y == x but instead one has x[-a[s]] == x[a[s]] == numeric(0), > which is rather > # unfortunate -- so far the best I have come up with is: > > as <- ifelse(length(a[s]),-a[s],TRUE) > y <- x[as] > > which, doesn't read well. Apologies if this has been aired previously... > > url: www.econ.uiuc.edu/~roger Roger Koenker > email [EMAIL PROTECTED] Department of Economics > vox: 217-333-4558 University of Illinois > fax: 217-244-6678 Champaign, IL 61820 > > ______________________________________________ > 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.
