> x<-arima.sim(n=1000,list(ar=c(0.1,0.12),ma=c(-0.6,0.7)))
> b=c(1:11)
> for(h in c(0:10))
+ {
+     c=0
+     for(i in c(1:1000-h))
+     {
+         c=x[i]*x[i+h]+c
+     }
+     b[h+1]=1/1000*c
+ }
Error in b[h + 1] <- 1/1000 * c : replacement has length zero