[R] Avoiding loops to spare time and memory
Dirk Enzmann
enzmann at kfn.uni-hannover.de
Thu May 8 10:58:29 CEST 2003
Is it possible to avoid the loop in the following function (or make the
function otherwise more efficient) and can someone point me to a
possible solution? (It would be great if hours could be reduced to
seconds :-).
# ---------------------------------------------
RanEigen=function(items=x,cases=y,sample=z)
{
X=matrix(rnorm(cases*items),nrow=cases,byrow=F)
S=crossprod(X-rep(1,cases) %*% t(colMeans(X)))
EV=eigen((1/sqrt(diag(S))*diag(items))%*%S%*%(1/sqrt(diag(S))*diag(items)),only.values=T)$values
for (i in 2:sample)
{
X=matrix(rnorm(cases*items),nrow=cases,byrow=F)
S=crossprod(X-rep(1,cases) %*% t(colMeans(X)))
EV=rbind(EV,eigen((1/sqrt(diag(S))*diag(items))%*%S%*%(1/sqrt(diag(S))*diag(items)),only.values=T)$values)
}
REigV=(cbind(1:items,colMeans(EV)))
REigV[,2]=as.numeric(formatC(REigV[,2],format="f",digits=7,flag="
",width=10))
colnames(REigV)=c(' ','Eigenvalue')
rownames(REigV)=rep('',items)
return(REigV)
}
# ---------------------------------------------
Thanks in advance,
Dirk
*************************************************
Dr. Dirk Enzmann
Criminological Research Institute of Lower Saxony
Luetzerodestr. 9
D-30161 Hannover
Germany
phone: +49-511-348.36.32
fax: +49-511-348.36.10
email: ENZMANN at KFN.uni-hannover.de
http://www.kfn.de
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