[R] How to find series of small numbers in a big vector?
Ed Holdgate
edholdgate at yahoo.com
Tue Jan 30 02:49:28 CET 2007
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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