R help - Apr 2009 - Discover significant change in sorted vector

Hi,

suppose I have a simple sorted vector like this:

a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46);

Is there a function in R, I can use to discover that from index 8 to  
index 11 the values are changing significantly?
The function should return a value pointing to one of the indices 8,  
9, 10 or 11. Any of them would be fine.
The difficulty is that there may be no big gap. I mean, indices 8 and  
11 are somehow "connected" by indices 9 and 10. So, it's not an
option
to just search for biggest difference between the values.

Perfect would be a function that is able to discover multiple changes  
if it is present in the data.

Thanks!!
Henning

Perhaps something about like this:

which(diff(a) > mean(diff(a)))

On Wed, Apr 22, 2009 at 8:27 AM, Hans-Henning Gabriel <
hanshenning.gabriel@gmail.com> wrote:
> Hi,
>
> suppose I have a simple sorted vector like this:
>
> a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46);
>
> Is there a function in R, I can use to discover that from index 8 to index
> 11 the values are changing significantly?
> The function should return a value pointing to one of the indices 8, 9, 10
> or 11. Any of them would be fine.
> The difficulty is that there may be no big gap. I mean, indices 8 and 11
> are somehow "connected" by indices 9 and 10. So, it's not an
option to just
> search for biggest difference between the values.
>
> Perfect would be a function that is able to discover multiple changes if it
> is present in the data.
>
> Thanks!!
> Henning
>
> ______________________________________________
> R-help@r-project.org 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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Hans-Henning Gabriel wrote:
> Hi,
>
> suppose I have a simple sorted vector like this:
>
> a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46);
>
> Is there a function in R, I can use to discover that from index 8 to 
> index 11 the values are changing significantly?
> The function should return a value pointing to one of the indices 8, 
> 9, 10 or 11. Any of them would be fine.
> The difficulty is that there may be no big gap. I mean, indices 8 and 
> 11 are somehow "connected" by indices 9 and 10. So, it's not
an option
> to just search for biggest difference between the values.
>
> Perfect would be a function that is able to discover multiple changes 
> if it is present in the data.
>
Hi Henning,
Is max(diff(a)) any good to you?

Jim

Try this:
> a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46);
> ix <- seq_along(a)
> library(strucchange)
> bp <- breakpoints(a ~ ix, h = 4)
> bp
         Optimal 3-segment partition:

Call:
breakpoints.formula(formula = a ~ ix, h = 4)

Breakpoints at observation number:
7 11

Corresponding to breakdates:
0.3684211 0.5789474
> plot(a ~ ix)
> lines(ix, fitted(bp))

On Wed, Apr 22, 2009 at 7:27 AM, Hans-Henning Gabriel
<hanshenning.gabriel at gmail.com> wrote:
> Hi,
>
> suppose I have a simple sorted vector like this:
>
> a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46);
>
> Is there a function in R, I can use to discover that from index 8 to index
> 11 the values are changing significantly?
> The function should return a value pointing to one of the indices 8, 9, 10
> or 11. Any of them would be fine.
> The difficulty is that there may be no big gap. I mean, indices 8 and 11
are
> somehow "connected" by indices 9 and 10. So, it's not an
option to just
> search for biggest difference between the values.
>
> Perfect would be a function that is able to discover multiple changes if it
> is present in the data.
>
> Thanks!!
> Henning
>
> ______________________________________________
> R-help at r-project.org 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.
>