Message-ID: <4D9F26A3.6060609@gmail.com>
Date: 2011-04-08T15:15:47Z
From: Duncan Murdoch
Subject: duplicates() function
In-Reply-To: <BANLkTimQEeXMPCjWaHuQZ74t8d0A_9XeyQ@mail.gmail.com>
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.duncan at 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
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
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> >