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 > > ______________________________________________ > [email protected] 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. > ______________________________________________ [email protected] 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.
