[R] unique with tolerance

[Bert Gunter]

... and if it Duncan's suggestion won't do, maybe approaching it via
clustering might be useful.
But do note that, as stated, the problem is not well defined, because
transitivity fails: consider

v <- c(1,2,3,4,5,10)

with a tolerance of <=2. Then 1 is the same as 2 and 3, 2 and 3 are
the same as 4, but 1 is not the same as 4, etc. Exactly what would you
choose as the "unique" values with this tolerance in this situation?

-- Bert

On Thu, Sep 6, 2012 at 9:47 AM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
> On 06/09/2012 6:48 AM, Michael Bach wrote:
>>
>> Dear R Users and Developers,
>>
>> I am trying to do the equivalent of
>>
>> v <- c(1,2,3,3,2,1,)
>> vu <- unique(v)
>>
>> for a vector such as
>>
>> v2 <- c(1.02, 2.03, 1.00, 3.04, 3.06)
>> vut <- ...
>>
>> As indicated in the subject, we need approximately unique values with a
>> defined
>> tolerance, i.e. for the v2 vector the resulting vut vector using a
>> tolerance of
>> .1 should return e.g.
>>
>> [1] 1.02 2.03 3.06
>>
>> Also, mean/min values instead of max could be returned.
>>
>> My actual question: Is there a convenience function or other mechanism
>> already
>> implemented that could do something similar?
>
>
> It might be enough to round your values before checking.  For the example,
>
> dups <- duplicated( round(v2) )
> v2[!dups]
>
> (This gives 3.04 rather than 3.06; I don't know if you care.)
>
> Duncan Murdoch
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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