Re: [R] How do I avoid a loop?

From: Erik Iverson <iverson_at_biostat.wisc.edu>
Date: Tue, 19 Jun 2007 09:28:41 -0500

One more variation on the solution, no idea how it compares in speed.

Using your x ...

 > ifelse(x, unlist(mapply(seq, to = rle(x)$lengths, from = 1)), 0) [1] 1 2 3 0 0 1 2 0 1

Feng, Ken 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
>
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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. Received on Tue 19 Jun 2007 - 15:13:25 GMT

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