>>>>> arun <smartpink...@yahoo.com>
>>>>> on Wed, 16 Jan 2013 19:20:46 -0800 writes:
> Hi,
> May be this helps:
> library(Matrix)
> res1<-lapply(split(x,1:nrow(x)),function(y)
sparseMatrix(i=rep(1:4,each=5),j=1:(4*5),x=y))
> do.call(rbind,lapply(seq_along(res1),function(i) res1[[i]][i,]))
> # [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[,13] [,14]
> #[1,] 1 5 9 13 17 0 0 0 0 0 0 0
0 0
> #[2,] 0 0 0 0 0 2 6 10 14 18 0 0
0 0
> #[3,] 0 0 0 0 0 0 0 0 0 0 3 7
11 15
> #[4,] 0 0 0 0 0 0 0 0 0 0 0 0
0 0
> # [,15] [,16] [,17] [,18] [,19] [,20]
> #[1,] 0 0 0 0 0 0
> #[2,] 0 0 0 0 0 0
> #[3,] 19 0 0 0 0 0
> #[4,] 0 4 8 12 16 20
Thank you for thinking of Matrix (the package, not the movie)
here.
If you do,
> x <- matrix(1:20, 4,5)
> require(Matrix)
the following is "a tiny bit" nicer, using the bdiag()
function which has been written to create block diagonal matrices.
> t(bdiag(split(x,1:nrow(x))))
4 x 20 sparse Matrix of class "dgCMatrix"
[1,] 1 5 9 13 17 . . . . . . . . . . . . . . .
[2,] . . . . . 2 6 10 14 18 . . . . . . . . . .
[3,] . . . . . . . . . . 3 7 11 15 19 . . . . .
[4,] . . . . . . . . . . . . . . . 4 8 12 16 20
>
and if you don't want a sparse matrix for some reason,
(and think twice: it may be more efficient to keep it !)
you wrap the result with a
as.matrix( <result> )
---
Martin Maechler, ETH Zurich
> ----- Original Message -----
> From: Kathryn Lord <kathryn.lord2...@gmail.com>
> To: r-help <r-help@r-project.org>
> Cc:
> Sent: Wednesday, January 16, 2013 9:11 PM
> Subject: [R] create block diagonal with each rows
> Dear R users,
> I'd like to create a block diagonal matrix with each rows in a matrix.
> Here is a simple example. (In fact, the matrix is big)
> x <- matrix(1:20, 4,5)
>> x
> [,1] [,2] [,3] [,4] [,5]
> [1,] 1 5 9 13 17
> [2,] 2 6 10 14 18
> [3,] 3 7 11 15 19
> [4,] 4 8 12 16 20
> With each rows in matrix x, I'd like to make the matrix below.
> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9][,10]
> [,11][,12][,13][,14][,15][,16][,17][,18][,19][,20]
> [1,] 1 5 9 13 17 0 0 0 0 0 0 0 0
> 0 0 0 0 0 0 0
> [2,] 0 0 0 0 0 2 6 10 14 18 0 0 0
> 0 0 0 0 0 0 0
> [3,] 0 0 0 0 0 0 0 0 0 0 3 7 11
> 15 19 0 0 0 0 0
> [4,] 0 0 0 0 0 0 0 0 0 0 0 0 0
> 0 0 4 8 12 16 20
> Any suggestion will be greatly appreciated.
> Best,
> Kathryn Lord
> [[alternative HTML version deleted]]
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> PLEASE do read the posting guide
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