[R] find the permutation function of a sorting

[John]

Thanks, David,  Rui and Jeff!!! The function order works much better.
I should have used an example where the permutation and its inverse are not
identical:

> i <- order(c("B", "C", "A"))
> i
[1] 3 1 2
> c("D","E", "F")[i]
[1] "F" "D" "E"
> c("D","E", "F")[order(i)]
[1] "E" "F" "D"

2018-05-23 14:18 GMT+08:00 Rui Barradas <ruipbarradas using sapo.pt>:

> Hello,
>
> Like David said, what you are trying to do with sort() can be done with
> order() in a much easier way.
>
> First, your code
>
> x <- sort(c("bc","ac","dd"), index.return=TRUE)
>
>
> Now, with function order()
>
>
> i <- order(c("bc", "ac", "dd"))
>
> y <- c("D","E", "F")[i]
> y
> #[1] "E" "D" "F"
>
> # This will give you the inverse,
> # just apply order() to the output of order(),
> # function order() is its own inverse
>
> y[ order(i) ]
> #[1] "D" "E" "F"
>
>
> Finally, compare the results and see that they are exactly the same.
>
> identical(x$ix, i)
> #[1] TRUE
>
>
> Hope this helps,
>
> Rui Barradas
>
> On 5/23/2018 4:37 AM, John wrote:
>
>> sort(c("bc","ac","dd"), index.return=TRUE)
>>>
>> $x
>> [1] "ac" "bc" "dd"
>>
>> $ix
>> [1] 2 1 3
>>
>>
>> We have the permutation, namely 1-->2, 2-->1, 3-->3.
>> How can I apply the permutation function to a new set
>> c("D","E", "F")?
>> so that the result is
>> c("E","D", "F").
>>
>>
>>
>>
>> 2018-05-23 11:06 GMT+08:00 David Winsemius <dwinsemius using comcast.net>:
>>
>>
>>>
>>> On May 22, 2018, at 10:57 PM, John <miaojpm using gmail.com> wrote:
>>>>
>>>> Thanks, David.
>>>> I got the answer from the web.
>>>> Is there any easy way to permute a set (e.g., a set of characters) by
>>>>
>>> the permutation it returns? Thanks,
>>>
>>>>
>>>>
>>>> x <- c(10,7,4,3,8,2)
>>>>> sort(x, index.return=TRUE)
>>>>>
>>>> $x
>>>> [1]  2  3  4  7  8 10
>>>>
>>>> $ix
>>>> [1] 6 4 3 2 5 1
>>>>
>>>>
>>> I don't understand what is being requested. The $ix value is the same as
>>> the one returned `by order`.
>>>
>>> David.
>>>
>>>
>>> 2018-05-23 10:49 GMT+08:00 David Winsemius <dwinsemius using comcast.net>:
>>>>
>>>>
>>>> On May 22, 2018, at 10:06 PM, John <miaojpm using gmail.com> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>>    Is there any way to find the permutation function of the sorting and
>>>>>
>>>> to
>>>
>>>> apply the function (or its inverse) elsewhere?
>>>>>
>>>>>    For example, the following permutation function from the sorting in
>>>>>
>>>> the
>>>
>>>> matrix form is
>>>>> c(1,2,3), c(2,1,3)
>>>>>
>>>>> sort(c("bc","ac","dd"))
>>>>>>
>>>>> [1] "ac" "bc" "dd"
>>>>>
>>>>>
>>>> I think you are asking for the `order` function.
>>>>
>>>>    I try to find it in the permutations/permute package, but I can't
>>>>>
>>>> find it
>>>
>>>>
>>>>> John
>>>>>
>>>>>        [[alternative HTML version deleted]]
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>         [[alternative HTML version deleted]]
>>
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