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Old 10-16-2012, 08:58 PM   #22
country flag amirbachar
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Default Re: Alternative player ranking system

Quote:
Originally Posted by G.100sic View Post
One possible concern in this methodology is would it cause an "inflation" of points over the time.

If we take a match result in sets, then a question is how to treat results in women's tennis, since all matches are played in "best of 2 sets". Should they be treated completely separately, or use criteria for male tennis? That is, treat win in 2 sets as 1, win 1 set = 0.5, or 2 sets = 0.66. The second approach would lead to significantly lower maximal rating for female players, and I think that is not fair.

There is also a matter of selecting a proper K constant. For my calculations I initially put this constant to 24, but there are some systems in chess which use different values for K depending of strength range, for instance higher K for rating below 2000, and lower K above 2000. K constant effectively determines the maximum difference in points that can result as an outcome of a single match.
My system doesn't cause infaltion of points over time. It just treats every set seperately if you look more closely... Similary, the maximum for women is not different then for men, since the ELO rating converges to the real difference.

Quote:
Originally Posted by G.100sic View Post
I looked up the Glicko system a bit... If the Elo ranking list is not used as an official ranking, for instance as a base for tournament seeding, then using Glicko is a bit of an overkill, don't you think?!
It is a bit o an overkill, but I think ELO does have a problem that it doesn't take into account the certainty of the rating for each player.
In chess they partly solve it by giving lower K factor to better players.

Quote:
Originally Posted by G.100sic View Post
One interesting thing I discovered...
Points in Elo system correlate well to ATP/WTA points as:
<Elo points> ~ 300*loge(<ATP/WTA points>)
In addition, the points ratio is a good approximation to the probabilties ratio in a head to head encounter. I read about it in www.heavytopspin.com.
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