Computerintensive Methoden - Simulation of the lines coalescing

From StatWiki

n=3

line = array(dim=c(n,n,n))
size = array(dim=c(n,n))
coal = array(dim=c(n))

for (j in 1:n) {
	line[n,j,1] <- j
	size[n,j] <- 1
}

for (i in 1:(n-3)) {
	coal <- sample(1:(n-i+1), 2, replace=F)
	coal <- sort(coal)
	for (j in 1:coal[2]-1) {
		for (ii in 1:size[n-i+1,j]) {
			line[n-i,j,ii] <- line[n-i+1,j,ii]
		}
		size[n-i,j] <- size[n-i+1,j]
	}
}
   

#

Error in 1:size[n - i + 1, j] : argument of length 0
Execution halted