On 08/04/2011 11:08 AM, Joshua Ulrich wrote:
How about:
y<- rep(NA,length(x))
y[duplicated(x)]<- match(x[duplicated(x)] ,x)
That's a nice solution for vectors. Unfortunately for me, I have a
matrix (which duplicated() handles by checking whole rows). So a better
example that I should have posted would be
x <- cbind(1, c(9,7,9,3,7) )
and I'd still like the same output
duplicated(x)
[1] FALSE FALSE TRUE FALSE TRUE
duplicates(x)
[1] NA NA 1 NA 2
Duncan Murdoch
--
Joshua Ulrich | FOSS Trading: www.fosstrading.com
On Fri, Apr 8, 2011 at 9:59 AM, Duncan Murdoch<murdoch.dun...@gmail.com> wrote:
> I need a function which is similar to duplicated(), but instead of returning
> TRUE/FALSE, returns indices of which element was duplicated. That is,
>
>> x<- c(9,7,9,3,7)
>> duplicated(x)
> [1] FALSE FALSE TRUE FALSE TRUE
>
>> duplicates(x)
> [1] NA NA 1 NA 2
>
> (so that I know that element 3 is a duplicate of element 1, and element 5 is
> a duplicate of element 2, whereas the others were not duplicated according
> to our definition.)
>
> Is there a simple way to write this function? I have an ugly
> implementation in R that loops over all the values; it would make more sense
> to redo it in C, if there isn't a simple implementation I missed.
>
> Duncan Murdoch
>
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