IIDX dan course clear rate

Reference:
http://www.geocities.jp/n_krsm/class.html

Not 100% accurate, so the actual value may vary by 1%.

Below, PG = pgreat, GR = great, GD = good, BD = bad, PR = poor (both regular
poors and excess poors), CB = combo breaks, EP = excess poor

note: EP = BD + PR - CB

All clear rates are rounded down.


Clear rate for individual songs
===============================

When a song is cleared
----------------------

Base value = (PG×110 + GR×109 + GD×80 - BD×260 - PR×425 - EP×500)% / note count
           = (PG×110 + GR×109 + GD×80 - BD×760 - PR×925 + CB×500)% / note count

Clear rate:
- Base value > 100 → clear rate = 100%
- Base value between 70 and 100 → clear rate = base value
- Base value between 55 and 70 → clear rate = (base value × 2) - 70
- Base value < 55 → clear rate = 40%

So the lowest possible clear rate for a clear is 40%.

When a song is failed
---------------------

Clear rate = (PG + GR + GD + CB)×40% / note count

That is, it's 40% × the fraction of total notes hit or missed where you died
(rounded down), so it can be between 0% and 39%.


Clear rate for whole course
===========================

It's just the average of the clear rates for each song in the course (rounded
down).

So in theory, the highest clear rate you can have on a failed course is
(100+100+100+39)/4 = 84%, and the lowest clear rate you can have on a pass is
(40+40+40+40)/4 = 40%.