Rating Mechanics

## Rating mechanics

The mechanics are subject to change as more data is collected and further variation and tunings are done

## The variables involved

EloGrade uses a variation of the Elo rating system, so the elements involved are the same:

Arbitrary starting rating: 1500. On EloGrade, when we know nothing about a photo we set them to 1500 rating.

Curve function used: cumulative distribution function, in particular cdf((ratings_difference) / (200 * SQRT(2)))

Expected win/loss ratios vs ratings based on the function:

Actual win/loss ratios vs ratings after trial runs:

The other important but somewhat arbitrary variable is the K factor. EloGrade uses a variable K factor: ((1100.0 / (n*1.5 + 6)).to_f + 6.0).to_i where n is number of comparisons done. So the K factor starts off very large as we know nothing about the photo, and decreases rapidly eventually converging to a very low K factor of 6. This is based on the belief that the rating of a photo is stable (unlike player or athlete skill which may change quickly and need to be reflected).