This is so basic that I could not get search words for googling, and similarly it took me 7.9 minutes to get a title for it. Embarrassed!
I thought the following must give me "error: subscript indices must be either positive integers or logicals."
A = 1:7.9 but it gives the same result as A = 1:7.1 so that it looks like A = 1:floor(7.9) I think 7.9 and 7.1 are not "positive integers".
Sorry for taking you so low down on this innocent Monday's morning!