[R] all possible samples

[apjaworski@mmm.com]

I am not sure if this is the easiest way, but you can do something like
this:

library(gregmisc)
combinations(N, n, x, repeats=TRUE)

where x is an atomic vector of size N.  The only restriction is that the x
vector has to have N unique elements.  The combinations function will
return a matrix with n columns containing the combinations.

The combinations function is defined recursively.  Even for moderate values
of N and n it will either take a long time or bomb out with the "evaluation
is nested too deeply" error.  For example, on my modest machine (PIII 1GHz
with 1/5 Gbyte of memory) it takes almost a minute to evaluate

combinations(30, 6, repeats=TRUE)   (1623160 combinations)

and

combinations(44, 2, repeats=TRUE)   (only 990 combinations)

bombs out.

If you need to work with larger numbers you will probably need a sequential
code.

Hope this helps,

Andy


__________________________________
Andy Jaworski
Engineering Systems Technology Center
3M Center, 518-1-01
St. Paul, MN 55144-1000
-----
E-mail: apjaworski at mmm.com
Tel:  (651) 733-6092
Fax:  (651) 736-3122


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  |      To:       R-help at stat.math.ethz.ch                                                                                     |
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  |      Subject:  [R] all possible samples                                                                                     |
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Dear all, there is an R function that return all possible samples of size
n,
with replacement,  from a vector of length N ?

Best regards

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