[R] How to repeat vectors ?

[Gabor Grothendieck]

Here are 4 approaches in order from most compact
to least.  #1 only works for numeric matrices, # 2 is
a shorter versio of your solution using rep.vec and # 3
is from Alex's post and is likely what I would
use in practice.

m <- matrix(1:4, 2) # test matrix

# 1 - m must be numeric for this one to work
kronecker(m, rep(1,2))

# 2
apply(m, 2, rep, each = 2) # 2

# 3 - from Alex's post
m[rep(1:nrow(m), each = 2),]

# 4
matrix(rbind(c(m), c(m)), nc = ncol(m))

On 9/30/06, Tong Wang <wangtong at usc.edu> wrote:
> I just figured out a way to do this:
>          rep.vec <- function(X,n)    return(t(array(rep(X,n),c(length(X),n))))
>
>   Then,    apply(MyMatrix, 2, rep.vec,2)
>
> Is there a better way ?  Is there an internal function to repeat a vector or matrix ?
>
> Thanks a lot.
>
>
> ----- Original Message -----
> From: Tong Wang <wangtong at usc.edu>
> Date: Friday, September 29, 2006 11:23 pm
> Subject: How to repeat vectors ?
> To: r-help at stat.math.ethz.ch
>
> > Hi,
> >    If I have a matrix  , say       a11   a12
> >                                                   a21  a22
> >    Is there a routine to get:      a11  a12
> >                                                     a11  a12
> >                                                     a21   a22
> >                                                     a21   a22
> >
> >     Thanks a lot for any help.
> >
> > best
> >
>
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