[R] selecting values that are unique, instead of selecting unique values

[Gabor Csardi]

Wow, that is smart, although is seems to be overkill..... 
I guess 'duplicated' is better than O(n^2), is it really?

Gabor

On Wed, Jun 25, 2008 at 05:43:30PM +0100, Prof Brian Ripley wrote:
> On Wed, 25 Jun 2008, Marc Schwartz wrote:
>
>> on 06/25/2008 11:19 AM Daren Tan wrote:
>>>
>>> unique(c(1:10,1)) gives 1:10 (i.e. unique values), is there any
>>> method to get only 2:10 (i.e. values that are unique) ?
>>>
>>
>> The easiest might be:
>>
>>> Vec
>> [1]  1  2  3  4  5  6  7  8  9 10  1
>>
>>> Vec[table(Vec) == 1]
>> [1]  2  3  4  5  6  7  8  9 10
>
> I don't think that is right: you are relying on recycling indices.  Try
>
> Vec <- c(1,1:10)
> Vec[table(Vec) == 1]
>
> which should be the same.
>
> I was about to write
>
> tab <- table(Vec)
> names(tab)[tab==1]
>
> but that gives a character vector.  Here's a different way:
>
> Vec[rowSums(outer(Vec, Vec, "=="))==1]
>
>
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
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-- 
Csardi Gabor <csardi at rmki.kfki.hu>    UNIL DGM