[R] How to delete repeated values in MCMC sampling and get index of unique values?

Bert Gunter gunter.berton at gene.com
Thu Jan 17 23:20:38 CET 2013


What answer is wanted for

c(1,1,1,2,3,1)   ?

Note that Duncan's  two suggestions below give different answers for this.

-- Bert

On Thu, Jan 17, 2013 at 1:59 PM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> On 13-01-17 4:50 PM, C W wrote:
>>
>> Dear list,
>> How do you delete repeated samples?  In MCMC, when your candidate value
>> has
>> been reject, so you remain on the same point, so you keep that value.
>>
>> Say I have this toy example,
>>
>>> c(1,6,6,6,3,5,4,4,2,3,5)
>>
>>
>> The 6 and 4 are repeated, I only want the index of the non-repeated
>> values.
>>
>> I thought of using which() and unique(), but that does not give you the
>> index of the unique values.
>
>
> You could use x[!duplicated(x)] or rle(x)$values, depending on your
> definition of "repeated".  I hope you're aware that you can't use either for
> things like quantiles and moments of the limiting distribution.
>
>> x <- c(1,6,6,6,3,5,4,4,2,3,5)
>> x[!duplicated(x)]
> [1] 1 6 3 5 4 2
>> rle(x)$values
> [1] 1 6 3 5 4 2 3 5
>
> Duncan Murdoch
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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