How to work on a single level hierarchy?

[mauriciolila]

I was wondering how I could specify a one-level hierarchy, for instance, a single State divided in Cities( 7 digits id ).
I was trying to pass the city argument as "characters=c(7)" and unfortunately I am getting the following outcome

data.hts<-hts(data.ts, bnames = colnames(data.ts),characters=c(7))
Error in substr(unique.str[[x]], start = 1L, stop = end[x - 1L]) :
invalid substring arguments