[R] Listing all possible samples of size n form a population

[(Ted Harding)]

On 08-Dec-05 Ales Ziberna wrote:
> Dear useRs!
> 
> I would like to list all possible samples of size n form a
> population of size N. Obviously, N must be small (up to 20??)
> for this to be possible.
> 
> For example, let say that N = 3 and n = 2. Therefore, we can
> say we have units 1, 2 and 3. I believe all possible samples
> are : {1,2},{2,3} and {1,3}.
> 
> I would like to emphasize that I am not looking for the number
> of different samples, but a list of all possible samples.

Install package "combinat" and use the function 'combn' therein:

> library(combinat)
> ?combn

> combn((1:3),2)
     [,1] [,2] [,3]
[1,]    1    1    2
[2,]    2    3    3

> combn((1:5),2)
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]    1    1    1    1    2    2    2    3    3     4
[2,]    2    3    4    5    3    4    5    4    5     5

> combn((1:5),3)
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]    1    1    1    1    1    1    2    2    2     3
[2,]    2    2    2    3    3    4    3    3    4     4
[3,]    3    4    5    4    5    5    4    5    5     5

and so on ...

Best wishes,
Ted.


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Date: 08-Dec-05                                       Time: 15:07:37
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