[R] "flipping" vector and matrix

Rainer M Krug
Tue, 23 Oct 2007 14:47:18 -0000

Hi Robin

I knew that something like arev was somewhere around.

Thanks

Rainer

Robin Hankin wrote:
> Hello
>
>
> for vectors, use rev()
>
> For matrices and arbitrary-dimensioned arrays,
> use arev() of the magic package:
>
>
>  > library(magic)
>  > b <- matrix(1:9,3,3)
>  > b
>      [,1] [,2] [,3]
> [1,]    1    4    7
> [2,]    2    5    8
> [3,]    3    6    9
>  > arev(b)
>      [,1] [,2] [,3]
> [1,]    9    6    3
> [2,]    8    5    2
> [3,]    7    4    1
>  >
>
>
>
>
>
>
> On 23 Oct 2007, at 11:45, 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
>>
>> ______________________________________________
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>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>  tel  023-8059-7743
>