[R] Create unique sets of 3 from a vector of IDs?

[G. Jay Kerns]

Dear Kingsford,

You are quite right, my mistake:

urnsamples(ID, size = 3, replace = FALSE, ordered = TRUE)

Thanks.
Jay


On Wed, Dec 3, 2008 at 12:04 AM, Kingsford Jones
<kingsfordjones at gmail.com> wrote:
> However, I believe Brandon was trying to get the permutations of size
> 3, rather than combinations.  Dylan provided a solution including
> repeats.  Here's one without:
>
>> library(gtools)
>> permutations(5, 3, LETTERS[1:5])
>      [,1] [,2] [,3]
>  [1,] "A"  "B"  "C"
>  [2,] "A"  "B"  "D"
>  [3,] "A"  "B"  "E"
>  [4,] "A"  "C"  "B"
>  [5,] "A"  "C"  "D"
>  [6,] "A"  "C"  "E"
>  [7,] "A"  "D"  "B"
>  [8,] "A"  "D"  "C"
>  [9,] "A"  "D"  "E"
> [10,] "A"  "E"  "B"
> [11,] "A"  "E"  "C"
> [12,] "A"  "E"  "D"
> [13,] "B"  "A"  "C"
> [14,] "B"  "A"  "D"
> [15,] "B"  "A"  "E"
> [16,] "B"  "C"  "A"
> [17,] "B"  "C"  "D"
> [18,] "B"  "C"  "E"
> [19,] "B"  "D"  "A"
> [20,] "B"  "D"  "C"
> [21,] "B"  "D"  "E"
> [22,] "B"  "E"  "A"
> [23,] "B"  "E"  "C"
> [24,] "B"  "E"  "D"
> [25,] "C"  "A"  "B"
> [26,] "C"  "A"  "D"
> [27,] "C"  "A"  "E"
> [28,] "C"  "B"  "A"
> [29,] "C"  "B"  "D"
> [30,] "C"  "B"  "E"
> [31,] "C"  "D"  "A"
> [32,] "C"  "D"  "B"
> [33,] "C"  "D"  "E"
> [34,] "C"  "E"  "A"
> [35,] "C"  "E"  "B"
> [36,] "C"  "E"  "D"
> [37,] "D"  "A"  "B"
> [38,] "D"  "A"  "C"
> [39,] "D"  "A"  "E"
> [40,] "D"  "B"  "A"
> [41,] "D"  "B"  "C"
> [42,] "D"  "B"  "E"
> [43,] "D"  "C"  "A"
> [44,] "D"  "C"  "B"
> [45,] "D"  "C"  "E"
> [46,] "D"  "E"  "A"
> [47,] "D"  "E"  "B"
> [48,] "D"  "E"  "C"
> [49,] "E"  "A"  "B"
> [50,] "E"  "A"  "C"
> [51,] "E"  "A"  "D"
> [52,] "E"  "B"  "A"
> [53,] "E"  "B"  "C"
> [54,] "E"  "B"  "D"
> [55,] "E"  "C"  "A"
> [56,] "E"  "C"  "B"
> [57,] "E"  "C"  "D"
> [58,] "E"  "D"  "A"
> [59,] "E"  "D"  "B"
> [60,] "E"  "D"  "C"
>
>
> Kingsford Jones
>
>
> On Tue, Dec 2, 2008 at 9:41 PM, G. Jay Kerns <gkerns at ysu.edu> wrote:
>> Dear Brandon,
>>
>> On Tue, Dec 2, 2008 at 10:46 PM, Dylan Beaudette
>> <dylan.beaudette at gmail.com> wrote:
>>> On Tue, Dec 2, 2008 at 7:42 PM, philozine <philozine at yahoo.com> wrote:
>>>> Dear all:
>>>>
>>>> This is one of those "should be easy" problems that I'm having great difficulty solving. I have a vector containing ID codes, and I need to generate a 3-column matrix that contains all possible combinations of three.
>>>>
>>>> For example, my ID vector looks like this:
>>>> A
>>>> B
>>>> C
>>>> D
>>>> E
>>>>
>>>> I need to generate a matrix that looks like this:
>>>> A B C
>>>> A B D
>>>> A B E
>>>> A C B
>>>> A C D
>>>> A C E
>>>> A D B
>>>> A D C
>>>> A D E
>>>
>>> Hi,
>>>
>>> Does this do what you want?
>>>
>>> expand.grid(letters[1:5], letters[1:5], letters[1:5])
>>>
>>>
>>> D
>>>
>>
>>
>> Have a look at urnsamples() in the prob package.
>>
>> ID <- LETTERS[1:5]
>> urnsamples(ID, size = 3, replace = FALSE, ordered = FALSE)
>>
>> Best,
>> Jay
>>
>>
>>
>>
>> ***************************************************
>> G. Jay Kerns, Ph.D.
>> Associate Professor
>> Department of Mathematics & Statistics
>> Youngstown State University
>> Youngstown, OH 44555-0002 USA
>> Office: 1035 Cushwa Hall
>> Phone: (330) 941-3310 Office (voice mail)
>> -3302 Department
>> -3170 FAX
>> E-mail: gkerns at ysu.edu
>> http://www.cc.ysu.edu/~gjkerns/
>>
>> ______________________________________________
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>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>



-- 

***************************************************
G. Jay Kerns, Ph.D.
Associate Professor
Department of Mathematics & Statistics
Youngstown State University
Youngstown, OH 44555-0002 USA
Office: 1035 Cushwa Hall
Phone: (330) 941-3310 Office (voice mail)
-3302 Department
-3170 FAX
E-mail: gkerns at ysu.edu
http://www.cc.ysu.edu/~gjkerns/