Skill Rating

Skill Rating is a ranking metric aimed at determining the actual skill of a player based on their performance on any song in-game. Skill Rating is unique to FFR, and is arguably the most accurate skill-based ranking system of any online rhythm game. 

Your Skill Rating is an incrementally increasing average of your top fifty scores. Your personal best score matters the most (3.92%), and your fiftieth best score matters the least (0.08%). Following the placement guidelines of the Official Tournaments, players who have less than 250 games played and 50 unique songs passed are not ranked. Your rating for each song is determined by the "AAA equivalency" formula.

AAA Equivalency Formula

Or essentially, X number of goods on Y difficulty is equivalent to a perfect score on Z difficulty.

Unlike the previous formula, rating is scaled by difficulty as well as good count. This allows the Skill Rating formula to calculate AAA equivalent scores with greater than 28 goods, and in some cases, well over 1000 goods. The constants used are the result of applying a learning algorithm to a set of data points accumulated by the Official Tournament division placement team and other community members.

History

The Skill Rating formula was initially released by Trumpet63, Silvuh and PrawnSkunk on February 16, 2015. The project has undergone numerous iterations since its inception, and continues to evolve.

The idea of a similar system was first considered by Trumpet63, who graphed players' PA on songs early in the 10th Official FFR Tournament, creating a curve he called the Zenith Curve. Later, the released version of the formula was created using data accumulated by the Official Tournament division placement team. Using this information, each qualifying score with less than 28 goods can be changed into a AAA-equivalent score, giving you the difficulty of the song on which you have essentially played with 0 goods. This difficulty is multiplied by one hundred to yield your rating.

Your final rating used to be calculated by sum of your four best scores (0.4*A+0.3*B+0.2*C+0.1*D), where A is your best score. There are plans to expand the influence of your rating beyond your four best scores. There is no way to reduce your rating, unless the difficulty of one of your top 4 songs is lowered, or you record a better combo score.

The Skill Rating system initially only included public songs, because token songs contained too many "problem songs" that contained spikes or quirks that made accurate difficulties hard to determine. However, the songs (Crowdpleaser, OMGWTFT0k3N, Party 4u "holy nite mix", The Wises Were Wrong, and PWND!) were later moved to difficulty-0, so they wouldn't be reflected in the Skill Rating formula. This allowed the system to begin including token songs as of April 3rd, 2015.