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Old 10-11-2012, 06:32 PM   #16
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Default Re: Alternative player ranking system

I had an error in formulas, some values were permuted. I corrected it, now calculations work as suggested. Thanks Litotes!
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Old 10-12-2012, 05:45 PM   #17
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Default Re: Alternative player ranking system

Amazingly, today I was thinking of doing the same thing myself.
My thinking is to treat each set separately, so a 2:1 is like a result of 0.666, but the value is doubled by the number of sets * K.
K is the constant of the system. which will be decided by what gives the best predictability to the rankings.
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Old 10-12-2012, 05:56 PM   #18
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Default Re: Alternative player ranking system

I was also thinking of using the Glicko2 ranking system, which is an improvement of ELO, and creating different set of rankings for each surface, otherwise the rankings will be biased by the surface played lately...
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Old 10-15-2012, 10:42 AM   #19
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Default Re: Alternative player ranking system

Quote:
Originally Posted by amirbachar View Post
Amazingly, today I was thinking of doing the same thing myself.
My thinking is to treat each set separately, so a 2:1 is like a result of 0.666, but the value is doubled by the number of sets * K.
K is the constant of the system. which will be decided by what gives the best predictability to the rankings.
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.
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Old 10-15-2012, 10:49 AM   #20
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Default Re: Alternative player ranking system

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Originally Posted by amirbachar View Post
I was also thinking of using the Glicko2 ranking system, which is an improvement of ELO, and creating different set of rankings for each surface, otherwise the rankings will be biased by the surface played lately...
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?!
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Old 10-15-2012, 10:56 AM   #21
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Default Re: Alternative player ranking system

One interesting thing I discovered...
Points in Elo system correlate well to ATP/WTA points as:
<Elo points> ~ 300*loge(<ATP/WTA points>)
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Old 10-16-2012, 08:58 PM   #22
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Default Re: Alternative player ranking system

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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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Old 10-16-2012, 09:01 PM   #23
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Default Re: Alternative player ranking system

Here is a good KRACH based ranking, developed by a statistican named Jeff Sackmann:
http://tennisabstract.com/jrank/atp.html
(the owner of the blog I gave before)
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Old 10-17-2012, 07:19 PM   #24
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Default Re: Alternative player ranking system

I've tried in the past to experiment with different ranking algorithms, but I will be developing my own when I get the time. Just for fun.
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Old 10-19-2012, 08:36 AM   #25
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Default Re: Alternative player ranking system

Quote:
Originally Posted by amirbachar View Post
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.
Amirbachar, if I understand this correctly, in your system you calculate every set independantly? If, say, two players played a match with a result 2:1 in sets, that is as if they played 3 matches, two of which won the first player?

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Originally Posted by amirbachar View Post
Here is a good KRACH based ranking, developed by a statistican named Jeff Sackmann:
http://tennisabstract.com/jrank/atp.html
(the owner of the blog I gave before)
As Mr Sackmann said himself in his blog, every ranking serves 2 main purposes, one is the entertainment (everybody wants to know who is the best), and the other is official - in tennis for tournament entry and seeding. So, since we can not aspire to the official use, what is left for us, amateurs, is just the entertainment part... . There are many ways to look at stuff, especially in statistics, and I welcome every effort.
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Old 12-24-2012, 10:26 PM   #26
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Default Re: Alternative player ranking system

I'll be giving my version of Elo rating system a try starting with the Abu Dhabi tournament. Although this is considered an exhibition tournament, its competitiveness is real, and so IMO is the meaning of the results. I decided to start with a "race rank" - starting with clear table for the season for all players, since I don't have the resources (time, mostly) to implement the full historical Elo ranking. I'm going to include all really competitive results - ATP tournaments not lower then 250-series, Davis Cup singles matches, Grand Slams, World Team Cup singles matches, Hopman Cup, and other serious exhibition tournaments like Abu Dhabi (suggestions are welcome).

The method I'll be using:
- every player starts with a clean sheet, 0 points;
- since in Elo rating only the difference in points is significant, and negative values of points are allowed in calculation, I will not introduce any starting bias;
- so, players who loose more often then not, will go into negative domain, while those who win will go into positive domain;
- I will be using a fixed K-factor of 24;
- I will normalize all results to the "best of two sets", meaning - 2:0 win in sets will be normalized to 1:0, and 2:1 win will be normalized to 1:0.5;
- consequently, matches in "best of three sets" will be normalized as - win of 3:0 to 1.5:0, 3:2 to 1.5:1;
- that way, matches in "best of three sets" (Slams, DC) will have a higher weight - effectively as if the K-factor was 36;
- and lastly, season will end with World Tour Championships.

So much for the start, and I'll see where this leads in the process... different tables for different surfaces, other possibilities for evaluating results, etc... Elo system is really very flexible, anything that maps to 0-1 range can be used for calculations: serve and return percentages, games won, points won, you name it!
I'm not a statistician by profession, so bare with me...
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Old 12-24-2012, 11:31 PM   #27
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Default Re: Alternative player ranking system

You can't add exho results.
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Old 12-25-2012, 05:48 PM   #28
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Yes I can, I can do whatever pleases me with my list!
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Old 12-25-2012, 05:55 PM   #29
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Seriously, the only measure of value for me is are the players motivated enough for a real competition. I will not count exhibition matches whose sole purpose is entertaining spectators. On the other hand, there is no reason not to include matches from tournaments like Abu Dhabi.
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Old 12-25-2012, 07:17 PM   #30
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Default Re: Alternative player ranking system

I already posted ELO Ratings including historical results:
http://www.menstennisforums.com/showthread.php?t=211663
I also tested it to make very them very predictive.

Feel free to make your own version if you wish, though...
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