>   change <- c(NA, diff(q1$..1))
> will be 1 when ..1 goes from FALSE
> to TRUE, -1 for TRUE to FALSE, 0 for no change, and NA
> for the first element.  You may find it convenient to
> change that NA to something else or to not deal with
> the first element after computing the diff.
>
>
This is very helpful, I did not know about the notation V$..1

I can find no documentation for it, but it works.

cheers
Worik

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