[R] matrix dimension and for loop

[Laurent Gautier]

On Tue, Apr 09, 2002 at 07:12:08PM +0200, Peter Dalgaard BSA wrote:
> Laurent Gautier <laurent at genome.cbs.dtu.dk> writes:
> 
> > On Tue, Apr 09, 2002 at 05:46:40AM -0700, sonchawan tamkaew wrote:
> > > Dear all,
> > > 
> > > My questions are that if I have
> > > 
> > > > x<-rnorm(50)
> > > > dim(x)<-c(10,5)
> > > > y=1:5
> > > > Z<-matrix(0,NROW(x),NROW(y))
> > > > for (j in 1:NROW(y)) Z[,j]<-x[,j]*y[j]
> > > 
> > > 1. Is there any other way to write this without 'for'
> > > loop?
> > 
> > 
> > Z <- x * y
> > 
> > seems to do the job....
> 
> Nope. Try it with x <- matrix(1,10,5) and see.


...right... it was 'y[j]' and not 'y[,j]' (blurry eyes... looking too long at the screen)


this is probably what everybody already gave:
(I receive r-help few hours before the first ones to receive it)


 x * matrix(y, ncol=ncol(x), nrow=nrow(x), byrow=T)


(I hope it work for good now... :)  )




L.







> 
> -- 
>    O__  ---- Peter Dalgaard             Blegdamsvej 3  
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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