[R] Rbind help needed

ripley@stats.ox.ac.uk ripley at stats.ox.ac.uk
Wed Nov 27 21:39:02 CET 2002

On Wed, 27 Nov 2002 Bayesianbay at aol.com wrote:

> Dear list
> I have a very simple question which is causing me problems!
> I have a matrix A and simply want to rbind this matrix together n times (n is a large number)
> How can I write this in R?
> I know I could do new<-rbind(z,z,z,...z) with z written n times but this will take forever as n is so large.

Is z a matrix too?  A more efficient way would be

dn <- dim(z)
new <- t(matrix(t(z), dn[2], dn[1]*n))

relying on recycling.  As the t's show, it works most naturally for cbind.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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