[R] Data manipulation problem

[moleps]

Dear R´ers.

I´ve got a dataset with age and year of diagnosis. In order to age-standardize the incidence I need to transform the data into a matrix with age-groups (divided in 5 or 10 years) along one axis and year divided into 5 years along the other axis. Each cell should contain the number of cases for that age group and for that period. 

I.e.
My data format now is
ID-age (to one decimal)-year(yearly data).

What I´d like is 


age 1960-1965 1966-1970 etc...
0-5 3 8 10 15
6-10 2 5 8 13
etc..


Any good ideas?

Regards,
M