[R] Discover significant change in sorted vector

[Hans-Henning Gabriel]

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