From owner-r-help@stat.math.ethz.ch Tue Dec 14 13:03:13 1999
Received: from stat.math.ethz.ch (majordom@hypatia.ethz.ch [129.132.58.23])
	by t2.mscf.uky.edu (8.8.5/8.8.5) with ESMTP id NAA09810
	for <mai@ms.uky.edu>; Tue, 14 Dec 1999 13:03:10 -0500 (EST)
Received: by stat.math.ethz.ch (8.9.1/8.9.1) id SAA14023
	for r-help-gang-use; Tue, 14 Dec 1999 18:15:59 +0100 (MET)
Received: (from daemon@localhost)
	by stat.math.ethz.ch (8.9.1/8.9.1) id SAA14017
	for <r-help@stat.math.ethz.ch>; Tue, 14 Dec 1999 18:15:58 +0100 (MET)
Received: from sophie(129.132.58.2), claiming to be "sophie.ethz.ch"
 via SMTP by hypatia, id smtpdAAAa003Qx; Tue Dec 14 18:15:50 1999
Received: (maechler@localhost) by sophie.ethz.ch (8.6.12/D-MATH-client) id SAA02889 for r-help@stat.math.ethz.ch; Tue, 14 Dec 1999 18:15:48 +0100
Received: (from daemon@localhost)
	by stat.math.ethz.ch (8.9.1/8.9.1) id PAA08253
	for <r-help@stat.math.ethz.ch>; Tue, 14 Dec 1999 15:12:23 +0100 (MET)
Received: from ln.nimh.nih.gov(156.40.248.2)
 via SMTP by hypatia, id smtpdAAAa0020p; Tue Dec 14 15:12:14 1999
Received: from localhost (mcw@localhost) by ln.nimh.nih.gov (980427.SGI.8.8.8/950213.SGI.AUTOCF) via SMTP id JAA24196; Tue, 14 Dec 1999 09:11:32 -0500 (EST)
Date: Tue, 14 Dec 1999 09:11:32 -0500 (EST)
From: Matthew Wiener <mcw@ln.nimh.nih.gov>
To: a s <datamanagement@email.com>
cc: r-help@stat.math.ethz.ch
Subject: Re: [R] Combinations
In-Reply-To: <385226496.945109840240.JavaMail.root@web07.pub01>
Message-ID: <Pine.SGI.3.96.991214090848.24011F-100000@ln.nimh.nih.gov>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-r-help@stat.math.ethz.ch
Precedence: bulk
Status: OR

Alex:  Bill Venables sent me these functions in response to a similar
query of mine a few months ago (you can find the full reply by searching
the R archives under the heading "avoiding loops, gaining generality"):


subsets <- function(r, n, v = 1:n) 
  if(r <= 0) NULL else 
if(r >= n) v[1:n] else 
rbind(cbind(v[1], Recall(r - 1, n - 1, v[-1])),      
Recall(r, n - 1, v[-1])) 

permutations <- function(n, v = 1:n) { 
 if(n == 1) 
   return(v[1])   
 X <- NULL 
  for(i in 1:n) 
    X <- rbind(X, 
               cbind(v[i], permutations(n - 1, v[-i]))) 
  X
} 

Hope this helps.

Matt

On Mon, 13 Dec 1999, a s wrote:

> I need some help here.
> >From a vector of variable length (say, c(A,B,C,D), I need to obtain all
> posible combinations (order doesn't matter) of the elements.
> I would like a function such as:
> function(x,c(A,B,C,D))
> to give a matrix (for x=3) like:
> A B C
> A B D
> A C D
> B C D
> 
> or for x=2
> A B
> A C
> A D
> B C
> B D
> C D
> 
> And so on.
> Any ideas??
> 
> Thank you,
> Alex Ahgarin
> Data Management
> I.R.W. Co.


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._