Oops, such an amateur mistake. Thanks a lot for your quick response.
Regards TP On 03/05/2015 06:49 PM, Prof Brian Ripley wrote:
On 05/03/2015 14:55, Tadeáš Palusga wrote:Hi, I'm using this mailing list for the first time and I hope this is the right one. I don't think that the following is a bug but it can be a performance issue. By my opinion, there is no need to filter by [w != 0] in last sum of weighted.mean.default method defined in src/library/stats/R/weighted.mean.R. There is no need to do it because you can always sum zero numbers and filtering is too expensive (see following benchmark snippet)But 0*x is not necessarily 0, so there is a need to do it ... see > w <- c(0, 1) > x <- c(Inf, 1) > weighted.mean(x, w) [1] 1 > fun.new(x, w) [1] NaNlibrary(microbenchmark) x <- sample(500,5000,replace=TRUE) w <- sample(1000,5000,replace=TRUE)/1000 * ifelse((sample(10,5000,replace=TRUE) -1) > 0, 1, 0) fun.new <- function(x,w) {sum(x*w)/sum(w)} fun.orig <- function(x,w) {sum(x*w[w!=0])/sum(w)} print(microbenchmark( ORIGFN = fun.orig(x,w), NEWFN = fun.new(x,w), times = 1000)) #results: #Unit: microseconds # expr min lq mean median uq max neval # ORIGFN 190.889 194.6590 210.08952 198.847 202.928 1779.789 1000 # NEWFN 20.857 21.7175 24.61149 22.080 22.594 1744.014 1000 So my suggestion is to remove the w != check Index: weighted.mean.R =================================================================== --- weighted.mean.R (revision 67941) +++ weighted.mean.R (working copy) @@ -29,7 +29,7 @@ stop("'x' and 'w' must have the same length") w <- as.double(w) # avoid overflow in sum for integer weights. if (na.rm) { i <- !is.na(x); w <- w[i]; x <- x[i] } - sum((x*w)[w != 0])/sum(w) # --> NaN in empty case + sum(x*w)/sum(w) # --> NaN in empty case } ## see note for ?mean.Date I hope i'm not missing something - I really don't see the reason to have this filtration here. BR Tadeas 'donarus' Palusga ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
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