[R] identifying a 'run' in a vector
jwiley.psych at gmail.com
Thu Jul 7 01:46:53 CEST 2011
If an "ordered run" means the difference is between the ith and ith +
1 position is 1, then:
out <- rle(diff(x))
?diff gives you the differences (i + 1) - (i), and then run length
encoding encodes how long a run of the same number is. In this case,
there first run is length 7.
rle() outputs a list. If you only want to consider runs that change
by 1, then use the "values" element of the list to select only those
out$values == 1
if it is not at the beginning of the vector, cumsum(out$lengths) can
help to find the right indices to extract your run.
Hope this helps,
On Wed, Jul 6, 2011 at 4:32 PM, B77S <bps0002 at auburn.edu> wrote:
> How can I discern which elements in x (see below) are in 'order', but more
> specifically.. only the 1st 'ordered run'?
> I would like for it to return elements 1:8... there may be ordered values
> after 1:8, but those are not of interest.
> x <- c(1, 2, 3, 4, 5, 6, 7, 8, 20, 21, 22, 45)
> Thanks for any suggestions.
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Ph.D. Student, Health Psychology
University of California, Los Angeles
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