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

[Rainer M Krug]

On Thu, Jun 4, 2009 at 12:36 PM, Patrick Burns <pburns at pburns.seanet.com> wrote:
> How about:
>
> order(x, runif(length(x)))

Thanks - that is really elegant.

Rainer

>
>
>
> Patrick Burns
> patrick at burns-stat.com
> +44 (0)20 8525 0696
> 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
>>>
>>
>>
>>
>



-- 
Rainer M. Krug, Centre of Excellence for Invasion Biology,
Stellenbosch University, South Africa