[R] To detect the location of duplicate values

[Charles C. Berry]

On Mon, 5 Jul 2010, Moohwan Kim wrote:

> Dear R family,
>
> I have a question about how to detect some duplicate numeric observations.
> Suppose that I have two variables dataset.
>
> order value
> 1  0.52
> 2  0.23
> 3  0.43
> 4  0.21
> 5  0.32
> 6  0.32
> 7  0.32
> 8  0.32
> 9  0.32
> 10 0.12
> 11 0.46
> 12 0.09
> 13 0.32
> 14 0.25
> ;
> Could you help me indicate where the duplicate observations in a row
> (e.g., 0.32) are?

I see you already have replies about duplicate() and unique(), which are 
very handy for the 'detect' part of your query.


But to list the locations of the duplciated elements, you might also 
benefit from using split() and Filter() like this:

> Filter( function(x) length(x)>1, split(order, value) )
$`0.32`
[1]  5  6  7  8  9 13


HTH,

Chuck



>
> best,
> moohwan
>
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Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901