Where a list of unique text labels are required (i.e., where simple numbering will not suffice) it can be useful to have a simple function that generates the required amount.
In practice, this is simple in R when N is 26 or less as the LETTERS object can be used for this purpose. For example, to get ten unique labels:
LETTERS[1:10]
This function works in a similar way but will add a second, third etc. letter where the value of N requires it.