On Aug 1, 2011, at 20:12 , monk wrote:
> dear all,
>
> i have a quite simple question, i want to fill up a Matrix like done in the
> following function,
> but the performance is very bad for large dimensions
> is there a way to do this like with apply or something similar?
>
>
> makeMatrix <- function(a, b,dim) {
> X=matrix(0,ncol=dim,nrow=dim)
>
>
>
> for (i in c(1:dim)){
> for (j in c(1:dim)) {
> if (i==j) {X[i,j]<-a}
> else { X[i,j]<- exp(( -1*abs(i-j))/(3*b)) }
> }
> }
> X
> }
>
I'd go for something like
X <- outer(1:dim, 1:dim, function(i,j) exp(-abs(i-j)/3/b))
diag(X) <- a
> --
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>
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--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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