[R] switching elements of a vector

[Gabor Grothendieck]

Try this:

> which(diff(a) > 0) + 1
[1]  2  6  9 12 14 15


On Mon, May 24, 2010 at 6:02 AM, speretti <sabrina.peretti at gmail.com> wrote:
>
> Hi,
>
> I would like to receive help for the following matter:
>
> If I'm dealing with a numeric vectors containing increasing elements.
> i.e.
>
> a<-c(1,2,2,2,2,3,3,3,4,4,4,5,5,6,7,7,7)
>
> There exist an efficient way to obtain an vector that indicates the position
> of the changing element of "a"?
> In this case it would be something like:
>
> index<-c(1,6,9,12,14,15)
>
> usually I'm used cycles to obtain boolean vectors of the same length of "a"
> indicating the changing elements ...later I've muliplied them for their
> numeric sequence and after that I've selected elements different from zero
> ...it is quite long...
> can you find an easier solution?
>
> Thank you for you help
> --
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