# [R] repeating rows or columns within a matrix

Thu Mar 21 23:30:57 CET 2002

```>>>>> "Juhana" == Juhana Vartiainen <juhana.vartiainen at labour.fi> writes:

Juhana> Hello
Juhana> Spse I have a matrix, say

Juhana> 1 2 3
Juhana> 4 5 6
Juhana> 7 8 9

Juhana> and I would like to expand it by repeating rows within the matrix, to
Juhana> get, if the repeating factor is 2, say:

Juhana> 123
Juhana> 123
Juhana> 456
Juhana> 456
Juhana> 789
Juhana> 789

Juhana> (or columnwise as well) . There must be a smart way of doing that?

Juhana,

you could try the kronecker product

> z <- matrix(1:9,ncol=3,byrow=T)
> z
[,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
> kronecker(z, c(1,1))
[,1] [,2] [,3]
[1,]    1    2    3
[2,]    1    2    3
[3,]    4    5    6
[4,]    4    5    6
[5,]    7    8    9
[6,]    7    8    9

Cheers,

Andreas

--
Andreas Kiermeier
Senior Biometrician
GPO Box 397, Adelaide, SA 5001, Australia
Ph:  +61 8 8303 6819
Fax: +61 8 8303 6761

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