[R] "flipping" vector and matrix

Katharine Mullen
Tue, 23 Oct 2007 14:37:09 -0000

sorry, just do rev on the columns (no t()):

> x
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
> apply(x,2,rev)
     [,1] [,2] [,3]
[1,]    7    8    9
[2,]    4    5    6
[3,]    1    2    3


On Tue, 23 Oct 2007, Katharine Mullen wrote:

> One way:
>
> > x<-1:9
> > rev(x)
> [1] 9 8 7 6 5 4 3 2 1
>
> for x as the matrix you gave:
> > x
>      [,1] [,2] [,3]
> [1,]    1    2    3
> [2,]    4    5    6
> [3,]    7    8    9
> >
> >
> > apply(t(x),1,rev)
>      [,1] [,2] [,3]
> [1,]    7    8    9
> [2,]    4    5    6
> [3,]    1    2    3
>
>
> On Tue, 23 Oct 2007, Rainer M Krug wrote:
>
> > Hi
> >
> > I have a vector
> >
> > x <- c(1, 2, 3, 4, 5)
> >
> > and I want to "flip" it around, i.e. I need
> >
> > 5, 4, 3, 2, 1
> >
> > Is there a ssolution apart from
> >
> > y <- x[length(x):1]
> >
> >
> > I am also looking for the same for a matrix M, i.e.
> >
> > 1 2 3
> > 4 5 6
> > 7 8 9
> >
> > should become
> >
> > 7 8 9
> > 4 5 6
> > 1 2 3
> >
> > again, I am using
> >
> > M[1:dim(M)[1], dim(M)[2]:1]
> >
> >
> > Thanks
> >
> > Rainer
> >
> > ______________________________________________
> > 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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