# [R] (no subject) (was: Permutations)

Robin Hankin rksh at soc.soton.ac.uk
Wed Jul 14 10:11:48 CEST 2004

```Jordi

try this

R> x <- c(1,2,3,  10,11,12,  41,42,43,  81,82,83)
R> dim(x) <- c(3,4)
R> x
[,1] [,2] [,3] [,4]
[1,]    1   10   41   81
[2,]    2   11   42   82
[3,]    3   12   43   83
R>  jj <- t(apply(x,1,sample))
R> jj
[,1] [,2] [,3] [,4]
[1,]    1   41   10   81
[2,]    2   11   82   42
[3,]   12    3   43   83
R> as.vector(jj)
R>
[1]  1 2 12 41 11 3 10 82 43 81 42 83

and I think that does what you want...

We take the vector, rearrange it into a matrix with three rows, then
sample *within* the rows,
then rearrange into a vector again.

There will be one forbidden permutation, namely the identity (which
may or may not be
desirable).

This method doesn't allow "intra block" permutations.

best

rksh

>  Dear R users,
>  First of all, thanks for the incredibly fast answers and help of
>Rolf, Marc and Robert.
>  Yes, I noticed that it was a lot of permutacions, but my intention
>was to make this process automatic and take only 5.000 - 10.000
>permutations. Therefore, I wanted only to take that "interesting
>permutations" with "some information" [inter-block permutations].
>  The reason why I'm interested in these permutations is because I'm
>using some packages of Bioconductor to analyse my data from some
>microarrays and I thought that perhaps could be interesting to see
>what happens when I permute my data and I compare it against the not
>permuted data.
>  Thanks again for your time and suggestions.
>
>Jordi Altirriba
>Ph. D. Student
>
>Hospital Clinic-Barcelona-Spain
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help

--
Robin Hankin
Uncertainty Analyst
Southampton Oceanography Centre
SO14 3ZH
tel +44(0)23-8059-7743
initialDOTsurname at soc.soton.ac.uk (edit in obvious way; spam precaution)

```