Here is a slight variation. The second line is unchanged from my prior solution but the first line is different. The previous one I posted was slightly more complex and took about 50% longer to run than this one:
xx <- (cumsum(!x) + 1) * x (seq_along(x) - match(xx, xx) + 1) * x > # performance testing > > f1 <- function(x) { + xx <- cumsum(diff(c(FALSE, x)) > 0) + (seq_along(x) - match(xx, xx) + 1) * x + } > > f2 <- function(x) { + xx <- (cumsum(!x) + 1) * x + (seq_along(x) - match(xx, xx) + 1) * x + } > > > f3 <- function(x) { + j <- 0 + for(i in seq_along(x)) x[i] <- if (x[i]) j <- j+1 else j <- 0 + x + } > > set.seed(1) > x <- sample(c(TRUE, FALSE), 100000, replace = TRUE) > system.time(out1 <- f1(x)) user system elapsed 0.10 0.02 0.12 > system.time(out2 <- f2(x)) user system elapsed 0.07 0.01 0.08 > system.time(out3 <- f3(x)) user system elapsed 1.65 0.00 1.72 > identical(out1, out2) [1] TRUE > identical(out1, out3) [1] TRUE On 6/19/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote: > xx is 1 in every position of the first run of TRUE, 2 in every > position in the 2nd run of TRUE and so on. The parenthesized > expression in the second line converts those to increasing > values and multiplying it by x zaps the garbage in the positions > that correspond to FALSE in x. > > xx <- cumsum(diff(c(FALSE, x)) > 0) > (seq_along(x) - match(xx, xx) + 1) * x > > > On 6/19/07, Feng, Ken <[EMAIL PROTECTED]> wrote: > > Hi, > > > > I start with an array of booleans: > > > > x <- c( TRUE, TRUE, TRUE, FALSE, FALSE, TRUE, TRUE, FALSE, TRUE ); > > > > I want to define an y <- f(x) such that: > > > > y <- c( 1, 2, 3, 0, 0, 1, 2, 0, 1 ); > > > > In other words, do a cumsum when I see a TRUE, but reset to 0 if I see a > > FALSE. > > > > I know I can do this with a very slow and ugly loop or maybe use apply, > > but I was hoping there are some R experts out there who can show me > > a cleaner/more elegant solution? > > > > Thanks in advance. > > > > - Ken > > > > ______________________________________________ > > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.