Tricky math in PSQL

Hey list,

I am having problems trying to figure out the best way to implement a
complicated function in PostgreSQL. I have tried my best to articulate
my problem here:

    http://pastebin.com/zwWmYMd0

To understand it mathematically is not so hard, but to express it in
PSQL syntax is hard for me.

I am aware that the views and functions I have may not be the most
efficient. I am open to suggestions for those too.

--
Kip Warner -- Senior Software Engineer
OpenPGP encrypted/signed mail preferred
http://www.thevertigo.com