On Aug 20, 2009, at 9:30 PM, Steven Kang wrote:
Hi all R users,
I am trying to extract elements from an array (x as shown below)
where the
difference between the consecutive elements does not equal 1.
The desired output is:
j = 6,17,27,38,58,69,79,90
However, the code below only returns:
j = 1,69,79,90
I am assuming that "cbind" function is not extracting all the elements
meeting the condition. In Matlab, j = [] (empty array) would append
all the
elements into this variable j if the conditions are met. I have also
tried
concatenating the elements (j <- c(1, x[i], x[i+1], x[length(x)]),
however
no luck..
x
[1] 6 7 8 9 10 11 12 13 14 15 16 17 27 28 29 30 31 32 33 34 35
36 37 38
58 59 60 61 62 63 64 65 66 67 68 69 79 80 81 82 83 84 85 86 87 88 89
90
i <- 1
j <- numeric()
while (i < length(x))
{
if (x[i] + 1 != x[i+1])
j <- cbind(1, x[i], x[i+1], x[length(x)])
# j <- c(1, x[i], x[i+1], x[length(x)])
i <- i+1
}
Please advise any solutions that may enlighten my problem.
Highly appreciate for your help in this matter in advance.
Steve
How about this:
Ind <- which(diff(x) != 1)
j <- x[c(1, sort(c(Ind, Ind + 1)), length(x))]
> j
[1] 6 17 27 38 58 69 79 90
See ?diff and ?which for more information.
HTH,
Marc Schwartz
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
