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

[Kingsford Jones]

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)
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> E-mail: gkerns at ysu.edu
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>
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