[R] select unique by multiple values

[Bert Gunter]

On Wed, Oct 9, 2013 at 11:49 AM, Berend Hasselman <bhh at xs4all.nl> wrote:
>
> On 09-10-2013, at 13:50, Ronald Peterson <ron at hub.yellowbank.com> wrote:
>
>> Hi,
>>
>> New to R here.  Lots of fun.  Still rather green though.
>>
>> I'd like to select unique items from a list that looks like this (for
>> example):
>>
>>> xyz
>> $x
>> [1] 8 6 9 0 0 3 9 7 1 9
>> $y
>> [1] 1 2 9 5 1 2 0 9 2 9
>> $z
>> [1] 5 6 9 0 5 1 1 7 3 4
>>
>> I'd like to select unique (x,y), while preserving association with z
>> values.  When there are duplicate (x,y) pairs, it doesn't really matter
>> which (x,y,z) triplet gets preserved - selecting the first would be fine,
>> but any other way to do it would be fine also.  It /would/ be handy to also
>> get a list of the rejected triplets, if that's possible.  Ideas?
>
> You could try this
>
> A <- cbind(xyz[[1]],xyz[[2]])
> A
>
> indx <- which(duplicated(A))
> indx
>
> lapply(xyz,function(u) u[-indx])
> lapply(xyz,function(u) u[indx])

or even

indx <- duplicated(A))
lapply(xyz,function(u) u[!indx])
lapply(xyz,function(u) u[indx])

Fear not logical indexing!

;-)

-- Bert

>
>
> Berend
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

(650) 467-7374