格子に順序

# １辺のノード数
n <- 4
# 次元
d <- 3
a <- array(1:(n^d),rep(n,d))
N <- 1:n

Na <- 1:(n-1)
Nb <- 2:n
tmp.list <- rep(list(N),d-1)
tmp.list[[d]] <- Na

tmpa <- expand.grid(tmp.list)-1
tmp.list[[d]] <- Nb
tmpb <- expand.grid(tmp.list)-1

Amat <- matrix(0,0,2)
for(i in 1:d){
	tmp <- 1:d
	tmp[i] <- d
	tmp[d] <- i
	u <- n^(0:(d-1))
	Amat <- rbind(Amat,cbind(a[apply(t(tmpa[,tmp]) * u,2,sum)+1],a[apply(t(tmpb[,tmp]) * u,2,sum)+1]))
}
Amat
library(igraph)
g <- graph.edgelist(Amat)
plot(g)