[R] Detect numerical series

[Carl Witthoft]

This was actually answered a couple times in StackOverflow.  Someone and 
I indpendently wrote up the following function, stolen directly from the 
source for rle().


# extended version of rle to find all sorts of sequences
# if incr=0, this is rle

seqle<- function (x,incr=1)
{
     if (!is.vector(x) && !is.list(x))
         stop("'x' must be an atomic vector")
     n <- length(x)
     if (n == 0L)
         return(structure(list(lengths = integer(), values = x),
             class = "rle"))
     y <- x[-1L] != x[-n] +incr
     i <- c(which(y | is.na(y)), n)
     structure(list(lengths = diff(c(0L, i)), values = x[i]),
         class = "rle")
}

<quote>
From: David Winsemius <dwinsemius_at_comcast.net>
Date: Sat, 11 Feb 2012 10:08:17 -0500
On Feb 11, 2012, at 10:01 AM, syrvn wrote:

 > Hello,
 >
 > I am struggling with detecting successive digits in a numerical series
 > vector.
 >
 > Here is an example:
 >
 > vec <- c(1, 15, 26, 29, 30, 31, 37, 40, 41)
 >
 > I want to be able to detect 29, 30, 31 and 40, 41.
 >
 > Then, I would like to delete the successive digits from the vector.
 >
 > 1, 15, 26, 29, 37, 40
   vec[ c(TRUE, !diff(vec) == 1) ]
#[1] 1 15 26 29 37 40

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