[R] Duplicated non contiguous element in a list

[Peter McMahan]

Maybe not the most efficient, but here's a vector-level solution:

non.contig.dupes <- function(x){
     is.dup <- x %in% x[duplicated(x)]
     is.con <- c(x[-length(x)]==x[-1],F) | c(F,x[-length(x)]==x[-1])
     is.dup & !is.con}


On Mar 16, 2007, at 11:14 AM, Bruno C.. wrote:


> Hello,
>
> Given a vector I would like to rapidly identify duplicated non  
> contiguous elements.
> Given for example
> c(1,    1,    2,   3,    2,   4,   5,   6,    4)
> I would like to get:
> FALSE FALSE TRUE FALSE TRUE TRUE FALSE FALSE TRUE
>
> In fact I need to check this on the columns of a matrix!
> I can do that of couse with loops but is there any function already  
> available?
>
> Thanks
>
>
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