[R] Non repetitive permutations/combinations of elements

Greg Snow Greg.Snow at intermountainmail.org
Mon May 8 23:45:37 CEST 2006


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 at intermountainmail.org
(801) 408-8111
 

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Nameeta Lobo
Sent: Monday, May 08, 2006 3:33 PM
To: r-help at 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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