# [R] [BioC] function to find coodinates in an array

Ana Conesa aconesa at ochoa.fib.es
Fri Aug 17 08:25:50 CEST 2007

```The arr.ind in the which function does the job very nicely!!!
Thank you everyone for the  suggestions!

Ana

>
>
>---- Mensaje Original ----
>De: marc_schwartz at comcast.net
>Para: m_olshansky at yahoo.com
>Asunto: Re: [BioC] [R] function to find coodinates in an array
>Fecha: Thu, 16 Aug 2007 21:53:44 -0500
>
>>If I am correctly understanding the problem, I think that this is
>what
>>you want:
>>
>>set.seed(1)
>>
>># Create a 3x3x3 array
>>ARR <- array(sample(100, 27), c(3, 3, 3))
>>
>>> ARR
>>, , 1
>>
>>     [,1] [,2] [,3]
>>[1,]   27   89   97
>>[2,]   37   20   62
>>[3,]   57   86   58
>>
>>, , 2
>>
>>     [,1] [,2] [,3]
>>[1,]    6   61   43
>>[2,]   19   34   88
>>[3,]   16   67   83
>>
>>, , 3
>>
>>     [,1] [,2] [,3]
>>[1,]   32   17   21
>>[2,]   63   51   29
>>[3,]   75   10    1
>>
>>
>># Get the ordered indices of the elements in the array
>>> order(ARR)
>> [1] 27 10 24 12 22 11  5 25  1 26 19 14  2 16 23  3  9 13  8 20 15
>21
>>[23] 18  6 17  4  7
>>
>>
>># Get the actual array elements in order
>>> ARR[order(ARR)]
>> [1]  1  6 10 16 17 19 20 21 27 29 32 34 37 43 51 57 58 61 62 63 67
>75
>>[23] 83 86 88 89 97
>>
>>
>># Now loop over the above and using which(), get the 3D indices
>>> t(sapply(ARR[order(ARR)], function(x) which(ARR == x, arr.ind =
>TRUE)))
>>      [,1] [,2] [,3]
>> [1,]    3    3    3
>> [2,]    1    1    2
>> [3,]    3    2    3
>> [4,]    3    1    2
>> [5,]    1    2    3
>> [6,]    2    1    2
>> [7,]    2    2    1
>> [8,]    1    3    3
>> [9,]    1    1    1
>>[10,]    2    3    3
>>[11,]    1    1    3
>>[12,]    2    2    2
>>[13,]    2    1    1
>>[14,]    1    3    2
>>[15,]    2    2    3
>>[16,]    3    1    1
>>[17,]    3    3    1
>>[18,]    1    2    2
>>[19,]    2    3    1
>>[20,]    2    1    3
>>[21,]    3    2    2
>>[22,]    3    1    3
>>[23,]    3    3    2
>>[24,]    3    2    1
>>[25,]    2    3    2
>>[26,]    1    2    1
>>[27,]    1    3    1
>>
>>
>>See ?which and take note of the arr.ind argument.
>>
>>HTH,
>>
>>Marc Schwartz
>>
>>
>>On Thu, 2007-08-16 at 19:21 -0700, Moshe Olshansky wrote:
>>> A not very good solution is as below:
>>>
>>> If your array's dimensions were KxMxN and the "linear"
>>> index is i then
>>> n <- ceiling(i/(K*M))
>>> i1 <- i - (n-1)*(K*M)
>>> m <- ceiling(i1/K)
>>> k <- i1 - (m-1)*K
>>>
>>> and your index is (k,m,n)
>>>
>>> I am almost sure that there is a function in R which
>>> does this (it exists in Matlab).
>>>
>>> Regards,
>>>
>>> Moshe.
>>>
>>> --- Ana Conesa <aconesa at ochoa.fib.es> wrote:
>>>
>>> > Dear list,
>>> >
>>> > I am looking for a function/way to get the array
>>> > coordinates of given
>>> > elements in an array. What I mean is the following:
>>> > - Let X be a 3D array
>>> > - I find the ordering of the elements of X by ord <-
>>> > order(X) (this
>>> > returns me a vector)
>>> > - I now want to find the x,y,z coordinates of each
>>> > element of ord
>>> >
>>> > Can anyone help me?
>>> >
>>> > Thanks!
>>> >
>>> > Ana
>>> >
>>
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>ormatics.conductor
>>

```