R help - Dec 2005 - Listing all possible samples of size n form a population of size N

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.





Thank you in advance for any suggestions.

Best,

Ales Ziberna

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.


--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 08-Dec-05                                       Time: 15:07:37
------------------------------ XFMail ------------------------------