Similar to isletter. Returns a vector the same length as the input string but with a true for each character that is a number and false otherwise.
The test here is for the ascii character set, so char(48:57) qualifies.
while a nice pedestriletto, it should be baptized ISDIGIT rather than ISNUMBER. ISNUMBER (traditionally) recognizes string elements that constitute a valid sscanf-able sequence, eg, 1.2e3
as usual, just a thought