[R] permutation within rows of a matrix

[Gavin Simpson]

On Wed, 2011-11-16 at 14:29 -0500, R. Michael Weylandt wrote:
> Suppose your matrix is called X.
> 
> ? sample
> X[sample(nrow(X)),]

That will shuffle the rows at random, not permute within the rows.

Here is an alternative, first using one of my packages (permute -
shameful promotion ;-) !:

mat <- matrix(sample(0:1, 100, replace = TRUE), ncol = 10)

require(permute)
perms <- shuffleSet(10, nset = 10)
## permute mat
t(sapply(seq_len(nrow(perms)), 
         function(i, perms, mat) mat[i, perms[i,]],
         mat = mat, perms = perms))

If you don't want to use permute, then you can do this via standard R
functions

perms <- t(replicate(nrow(mat), sample(ncol(mat))))
## permute mat
t(sapply(seq_len(nrow(perms)), 
         function(i, perms, mat) mat[i, perms[i,]],
         mat = mat, perms = perms))

HTH

G

> Michael
> 
> On Wed, Nov 16, 2011 at 11:45 AM, Juan Antonio Balbuena <balbuena at uv.es> wrote:
> > Hello
> > This is probably a basic question but I am quite new to R.
> >
> > I need to permute elements within rows of a binary matrix, such as
> >
> >     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
> >  [1,]    0    0    0    0    1    0    0    0    0     0
> >  [2,]    0    0    1    1    0    0    0    1    1     0
> >  [3,]    0    1    0    0    0    0    1    0    0     0
> >  [4,]    0    0    0    0    0    0    1    1    0     0
> >  [5,]    0    0    0    1    0    0    0    0    1     0
> >  [6,]    0    0    1    1    0    0    0    0    0     1
> >  [7,]    0    0    0    0    0    0    0    0    0     0
> >  [8,]    1    1    0    1    0    0    0    1    0     1
> >  [9,]    1    0    0    1    0    1    0    1    0     0
> > [10,]    0    0    0    0    0    0    0    1    0     1
> >
> >
> > That is, elements within each row are permuted freely and independently from
> > the other rows.
> >
> > I see that is is workable by creating a array for each row, performing
> > sample and binding the arrays again, but I wonder whether there is a more
> > efficient way of doing the trick.
> >
> > Any help will be much appreciated.
> >
> >
> >
> > --
> > View this message in context: http://r.789695.n4.nabble.com/permutation-within-rows-of-a-matrix-tp4076989p4076989.html
> > Sent from the R help mailing list archive at Nabble.com.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

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