[R] How to find series of small numbers in a big vector?

[Jonne Zutt]

I suggest the following appraoch

This gives TRUE for all data within the search_range
        A1 = my_data > search_range[1] & my_data < search_range[2]

which() gives us the indices
        A2 = which(A1)

and diff() the gaps between those intervals
        A3 = diff(A2)

Hence, if A3 > search_length, we have enough consecutive numbers within
the search range

Finally, this is what you wanted to know?

        A2[ which(A3 > search_length) ]


On Mon, 2007-01-29 at 17:49 -0800, Ed Holdgate wrote:
> Hello:
> 
> I have a vector with 120,000 reals
> between 0.00000 and 0.9999
> 
> They are not sorted but the vector index is the 
> time-order of my measurements, and therefore
> cannot be lost.
> 
> How do I use R to find the starting and ending 
> index of ANY and ALL the "series" or "sequences" 
> in that vector where ever there are 5 or more  
> members in a row between 0.021 and 0.029 ?
> 
> For example:
> 
> search_range <- c (0.021, 0.029) # inclusive searching
> search_length <- 5   # find ALL series of 5 members within search_range
> my_data <- c(0.900, 0.900, 0.900, 0.900, 0.900,
>              0.900, 0.900, 0.900, 0.900, 0.900,
>              0.900, 0.028, 0.024, 0.027, 0.023,
>              0.022, 0.900, 0.900, 0.900, 0.900,
>              0.900, 0.900, 0.024, 0.029, 0.023,
>              0.025, 0.026, 0.900, 0.900, 0.900,
>              0.900, 0.900, 0.900, 0.900, 0.900,
>              0.900, 0.900, 0.900, 0.900, 0.022,
>              0.023, 0.025, 0.333, 0.027, 0.028,
>              0.900, 0.900, 0.900, 0.900, 0.900)
> 
> I seek the R program to report: 
> start_index of 12 and an end_index of 16
> -- and also --
> start_index of 23 and an end_index of 27
> because that is were there happens to be
> search_length numbers within my search_range.
> 
> It should _not_ report the series at start_index 40
> because that 0.333 in there violates the search_range.
> 
> I could brute-force hard-code an R program, but
> perhaps an expert can give me a tip for an
> easy, elegant existing function or a tactic 
> to approach?
> 
> Execution speed or algorithm performance is not, 
> for me in this case, important.  Rather, I
> seek an easy R solution to find the time windows 
> (starting & ending indicies) where 5 or more 
> small numbers in my search_range were measured 
> all in a row.
> 
> Advice welcome and many thanks in advance.
> 
> Ed Holdgate
> 
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