On Wed, 27 Jan 2010, Gregory Gentlemen wrote:
Dear R-users,
Say that I have a sequence of zeroes and ones:
x <- c(1,1,1,0,0,0,0,1,1,1,0,0,0,0,1,1,1,0,0,0,0)
The sequences of ones represent segments and I want to report the
starting and endpoints of these segments. For example, in 'x', the first
segment starts at location 1 and ends at 3, and the second segment
starts at location 8 and ends at location 10. Is there an efficient way
of doing this in R without having to right a bunch of if-else
conditions? I know the rle function will report the length of the
segments but not the endpoints.
If this is more than a small one-off problem you might try this:
require(IRanges) # from BioConductor
IRanges(Rle(x)==1) # n.b. Rle != rle
IRanges of length 3
start end width
[1] 1 3 3
[2] 8 10 3
[3] 15 17 3
HTH,
Chuck
Thanks in advance.
Gregory Gentlemen
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