data statistic functions

Hullo List,

What does Postgres offer in terms of statistics support (not the
statistics about the database, but functions to operate on the data).

I know there are simple things like AVG, COUNT, MAX, and MIN, but what else?

I'm not sure where to begin looking, other than a cursory inspection of
http://www.postgresql.org/docs/8.3/static/functions.html . . .

On a side note, I also noted that I couldn't immediately spot AVG, MAX,
or MIN in the output of \df.

Thanks,

Kevin