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2006 Oct 24
3
Help with understanding [[]] [] array, list, matrix referencing
...the 
R guides and several tutorials but I am not the fastest kid on the block 
so I am still having difficulty understanding this.  For examples the 
following code produces a 5 element list of 2X5 random numbers that I 
then convert to a 2X5X5 matrix.
cov<-matrix(c(.4,-.1,-.1,.3),nrow=2,ncol=2)
rnds<-NULL;
for (i in 1:5){
	t1<-rnorm(5,cov)
	t2<-rnorm(5,cov)
	t3<-rbind(t1,t2)
	rnds[i]<-list(t3)
}
rnds.matrix<-array(unlist(rnds),dim=c(2,5,5));
To access the matrix rnds.matrix I use rnds.matrix[x,y,z].  This I 
understand.
To access the list I user [[z]][x,y].  This I do not...