[R] making groups

[Mag. Ferri Leberl]

Dear everybody!
If I have an array of numbers e.g. the points my students got at an
examination, and a  key to group the numbers, e.g. the key which
interval corresponds with which mark (two arrays of the same length or
one 2x(number of marks)), how can I get the array of absolute
frequencies of marks?
I hope I have expressed my problem clearly.
Thank you in advance.
Mag. Ferri Leberl