Re: [R] Non repetitive permutations/combinations of elements

From: Greg Snow <Greg.Snow_at_intermountainmail.org>
Date: Tue 09 May 2006 - 07:45:37 EST


Try expand.grid:

expand.grid( c(-1,1), c(-1,1), c(-1,1) )

--

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow@intermountainmail.org
(801) 408-8111  

-----Original Message-----

From: r-help-bounces@stat.math.ethz.ch
[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Nameeta Lobo Sent: Monday, May 08, 2006 3:33 PM
To: r-help@stat.math.ethz.ch
Subject: [R] Non repetitive permutations/combinations of elements

Hello all,

I am trying to create a matrix of 1s and -1s without any repetitions for a specified number of columns.
e.g. 1s and -1s for 3 columns can be done uniquely in 2^3 ways.
-1 -1 -1
-1 -1 1
-1 1 -1
-1 1 1
 1 -1 -1
 1 -1 1
 1 1 -1
 1 1 1
and for 4 columns in 2^4 ways and so on.

I finally used the function combn([0 1],3) that I found at the following link
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId =7147&objectType=FILE
written by Jos van der Geest in Matlab which generated the above.

How can I do this is R? I have looked at permn and combn in the combinat library and permutations and combinations in the gtools library and I am still confused as to how to get it to work.

Any suggestions will be truly appreciated.

Thank you

Nameeta



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