On Thu, 21 Aug 2008, Martin Maechler wrote:
Duh!!The simplest, probably fastest and most elegant solution of course is order(x, -y)
Only for numeric x. As Martin knows, I am working on ideas for 'generic' order, and one is a xtfrm(z) function that creates an integer vector that sorts the same as z. Then -xtrfm(z) would work.
...... if only I would have biked home earlier, today,... I'm sure I would have save much of my time.... Martin"MM" == Martin Maechler <[EMAIL PROTECTED]> on Thu, 21 Aug 2008 19:41:51 +0200 writes:MM> I've found the need to compute a version of order(x,y) MM> where I want the sort order for *increasing* x and MM> *decresing* y ... MM> something we could imagine could be provided in the MM> future as MM> order(x,y, decreasing = c(FALSE, TRUE)) MM> i.e., using a 'vectorized' decreasing argument. {No, MM> I'm not volunteering right now!} MM> I've found the following R-level solution and like to MM> quiz you for more elegant / faster solutions {but I am MM> not really interested in replacing order(x) by MM> sort.list(x, method="quick") and similar things; one MM> thing to consider *is* using an 'na.last = . ' MM> correctly, and I haven't had the need for that and so MM> not bothered to "do it"} MM> ## Here's a script with my version and a small example MM> ## (if you want speed comparisons, use larger examples) MM> : MM> orderXuYd <- function(x,y) { ## Purpose: order(x,y): x MM> up, y down ## MM> ---------------------------------------------------------------------- MM> ## Arguments: x,y: vectors of the same length ## MM> ---------------------------------------------------------------------- MM> ## Author: Martin Maechler, Date: 21 Aug 2008 MM> ix <- order(x) xx <- x[ix] iy <- tapply(y[ix], xx, MM> order, decreasing = TRUE) ## Note: 'SIMPLIFY', MM> 'USE.NAMES', 'use.names' are just for efficiency: MM> unlist(mapply(`[`, split(ix,xx), iy, SIMPLIFY = FALSE, MM> USE.NAMES = FALSE), use.names = FALSE) } MM> x <- c(1, 1, 2, 0, 0, 2, 1, 2, 2, 0, 2) y <- c(27, 21, MM> 45, 11, 13, 58, 35, 74, 95, 16, 122) ii <- MM> orderXuYd(x,y) ## yes, this is it : cbind(ii=ii, MM> x=x[ii],y=y[ii]) MM> ------------------ MM> Yes, the real reason this goes to R-devel is that it MM> might be neat to provide this (well, its generalization) MM> via an enhanced order() function. MM> Martin Maechler, ETH Zurich MM> PS: I will be basically offline all day tomorrow, so MM> don't expect my reactions to your ideas quickly MM> ______________________________________________ MM> R-devel@r-project.org mailing list MM> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
