Re: [R] elements that appear only once

From: Adaikalavan Ramasamy <ramasamy_at_cancer.org.uk>
Date: Wed 22 Feb 2006 - 23:27:19 EST

A slight variation on your solution but hopefully more readable:

        names( which( table(a) == 1 ) )

Regards, Adai

On Wed, 2006-02-22 at 09:11 +0000, Robin Hankin wrote:
> Hi.
>
> I have a factor and I want to extract just those elements that appear
> exactly once.
> How to do this?
>
> Toy example follows.
>
> > a <- as.factor(c(rep("oak",5) ,rep("ash",1),rep("elm",1),rep
> ("beech",4)))
> > a
> [1] oak oak oak oak oak ash elm beech beech beech beech
> Levels: ash beech elm oak
> > table(a)
> a
> ash beech elm oak
> 1 4 1 5
> >
>
> So I would want "ash" and "elm", because there is only one ash and
> only one elm in my wood.
>
> My Best Effort:
>
>
> > names(table(a)[table(a)==1])
> [1] "ash" "elm"
> >
>
> This doesn't seem particularly elegant to me; there must be a better
> way!
>
> anyone?
>
>
>
>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
>
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Feb 22 23:41:04 2006

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