From: Gabor Grothendieck <ggrothendieck_at_myway.com>

Date: Thu 15 Jul 2004 - 02:47:07 EST

R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 15 02:56:15 2004

Date: Thu 15 Jul 2004 - 02:47:07 EST

As Erich points out, there is some question as to what the original problem really is but lets assume its as Erich describes. Then, to get a random ordered permutation we just get a random permutation of 12 elements and sort the intra-block elements like this:

c(apply(matrix(sample(12,12),3),2,sort))

Note that there are 12! = 479,001,600 permutations
of 12 elements and 3!^4 = 1,296 of those
permutations correspond to each ordered

permutation so there are 479,001,600 / 1,296 =
369,600 ordered permutations in all.

Erich Neuwirth <erich.neuwirth <at> univie.ac.at> writes:

*:
*

: Perhaps what you want might better be described as

*: ordered partitions?
**:
**: Is what you want the following:
**:
**: We study sequences of length 12 and divide them in
**: 4 segments
**: position 1 2 3, position 4 5 6,
**: position 7 8 9, position 10 11 12,
**:
**: Find all permutation sequences of the numbers 1 to 12
**: with the property that all segment sequences
**: are monotonically increasing.
**:
**: I think that produces what you need.
**: Since the segments are ordered, you avoid intra-block permutations.
**:
**: If that is what you want, writing a recursive function should not be
**: too hard.
**:
**: Jordi Altirriba Gutiérrez wrote:
**:
**: > Dear R users,
**: > I’m a beginner user of R and I’ve a problem with permutations that I
**: > don’t know how to solve. I’ve 12 elements in blocks of 3 elements and I
**: > want only to make permutations inter-blocks (no intra-blocks) (sorry if
**: > the terminology is not accurate), something similar to:
**: >
**: > 1 2 3 | 4 5 6 | 7 8 9 | 10 11 12 ----------1st permutation
**: >
**: > 1 3 2 | 4 5 6 | 7 8 9 | 10 11 12 NO
**: > - -
**: > 3 2 1 | 4 5 6 | 7 8 9 | 10 11 12 NO
**: > - - -
**: > 1 2 4 | 3 5 6 | 7 8 9 | 10 11 12 YES-----2nd permutation
**: > - -
**: > 4 5 6 | 1 2 3 | 7 8 9 | 10 11 12 YES-----3rd permutation
**: > - - - - - -
**: > 4 5 6 | 2 1 3 | 7 8 9 | 10 11 12 NO
**: > - -
**: > ....
**: >
**: > Thanks for your time,
**: >
**: > Jordi Altirriba
**: > Ph D student
**: >
**: > Hospital Clinic – Barcelona - Spain
**: >
**: >
**: > MSN Motor. http://motor.msn.es/researchcentre/
**: >
**: > ______________________________________________
**: > R-help <at> stat.math.ethz.ch mailing list
**: > https://www.stat.math.ethz.ch/mailman/listinfo/r-help
**: > PLEASE do read the posting guide!
**: > http://www.R-project.org/posting-guide.html
**: >
*

:

R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 15 02:56:15 2004

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