st: Collapseing by year

[Lars Folkestad <lfolkestad@health.sdu.dk>]

Dear List

I have a dataset where i have patient id and birth year.
I would like to have my data set up so that i have

Birth year  number_of_persons_born_this_year


I think i have to use the collapse function, but i cannot figure out how.

Thank you.

lars


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