[R] How do I avoid a loop?

[Feng, Ken]

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