[R] order() with randomised order in ties?

[Patrick Burns]

How about:

order(x, runif(length(x)))



Patrick Burns
patrick at burns-stat.com
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http://www.burns-stat.com
(home of "The R Inferno" and "A Guide for the Unwilling S User")

Rainer M Krug wrote:
> Sorry for replying to my own post, but I found a solution. Still, a
> more elegant solution would be preferred.
> 
> On Thu, Jun 4, 2009 at 12:02 PM, Rainer M Krug <r.m.krug at gmail.com> wrote:
>> Hi
>>
>> I want to use order() to get the order of a vector.
>>
>> But I would need a different behavior when ties occur: similar to the
>> parameter  ties.method = "random" in the rank() function, I would need
>> to randomise the ties. Is this possible?
> 
> The solution is to randomize the vector before submitting to order():
> 
> x <- rep(1:10, 2)
> 
> iS <- sample( length(x) )
> o <- order( x[iS], na.last=NA, decreasing=TRUE)
> o
>  [1]  8 16 12 17  2  9  7 15 10 11  4 14  3  5 13 20  1  6 18 19
> x[iS][o]
>  [1] 10 10  9  9  8  8  7  7  6  6  5  5  4  4  3  3  2  2  1  1
> 
> iS <- sample( length(x) )
> o <- order( x[iS], na.last=NA, decreasing=TRUE)
> o
>  [1] 14 19 13 20  2 18  3 10  1 15  4  9 11 12  6  7  8 16  5 17
>> x[iS][o]
>  [1] 10 10  9  9  8  8  7  7  6  6  5  5  4  4  3  3  2  2  1  1
> 
> 
> Thanks
> 
> Rainer
> 
>> Example:
>>
>> x <- rep(1:10, 2)
>> order(x)
>>  [1]  1 11  2 12  3 13  4 14  5 15  6 16  7 17  8 18  9 19 10 20
>> order(x)
>>  [1]  1 11  2 12  3 13  4 14  5 15  6 16  7 17  8 18  9 19 10 20
>>
>> ## I would need different "order" for the ties, as below in rank() example:
>>
>> rank(x, ties.method="random")
>>  [1]  1  4  6  7 10 12 13 15 18 19  2  3  5  8  9 11 14 16 17 20
>>> rank(x, ties.method="random")
>>  [1]  2  4  5  7  9 12 14 15 18 19  1  3  6  8 10 11 13 16 17 20
>>
>>
>> Thanks
>>
>> Rainer
>>
>> --
>> Rainer M. Krug, Centre of Excellence for Invasion Biology,
>> Stellenbosch University, South Africa
>>
> 
> 
>