Change to the rating system

This thread highlights some problems with the current rating system which I am about to address.

http://www.redhotpawn.com/board/showthread.php?id=575

The key point is that new joiners to the site need some time to 'find their level'. Also, established members currently have good reason to avoid playing new members because it may reflect inaccurately on their own rating should the new joiner be of a high-standard.

For this reason I intend to change the system so that players with fewer than 20 completed games will be assigned a 'provisional' rating, and so that established players are not put-off playing new joiners.

Here is what I intend. It closely resembles other chess rating systems so should be familiar to many players already. Note that the main calculation is unchanged - all that differs is the way that new players affect the ratings.

1) For the first 20 games you play on RHP, your rating is calculated as an average of all your results. Each result is scored by adding 400 to your opponent's rating if you win, subtracting 400 from your opponent's rating if you lose, and copying your oponnent's rating if you draw. The exception to this is if your opponent has also played fewer than 20 games, in which case subsitute the value 200 for the 400s above.

2) If your opponent has played fewer than 5 games, then their rating will be treated as 1200 for the sake of the calculating your rating, even though their current provisional rating may not actually be 1200.

3) Once you have played 20 games, the rating is calculated using the
formula...

CR + (K * (S - WE)) * PA

Where...

CR = Your Current Rating
K = 32, unless your rating > 2100, then K = 24, unless your rating > 2400, then K = 16

S = Score (Win=1, Draw=0.5, Loss = -1)

WE = Win Expectancy. This is calcualted as 1 / (10^(RD/400) + 1) where RD is the difference (positive) between yours and your opponent's rating.

PA = Provisional Adjustment. If you opponent has played fewer than 20 games, then PA = 0.5, otherwise PA = 1

All thoughts welcome...

Thank you for making these adjustments. This is also a particularly elegant system, although I am not sure how much it differs from others. good work.

This seems a very sensible change. I'm not sure about the formula, but the new system should enable newcomers to gain an accurate rating much more quickly than present.

Good work, Chris 😀

Dave

I think an adjustment is in order...

Please add 400pts to my rating... 😛

Actually, it looks like a sensible adjustment to me. 🙂

Hmm. Seems a possibly bit wrong that our provisional ratings could go up when we lose. Could a newbie gain an average rating of 1600 by playing 20 games against an opp with a 2000 rating and losing them all?

If you are worried about this (you may well not be 🙂), perhaps the rating added to the average in the first 20 games, if the newcomer loses, should be something like min(opps_rating - 400, newbies_rating - 50)

Good work Chris!This was long overdue.

Sounds sensible. I wonder how it will affect me. I have completed 15 games and earned a rating of 1322. Will my rating be recalculated or will the new system just apply to the next 5 games?

Let's see: 8 wins, 2 losses against newbies. Say 8 x 1400, 2 x 1000
3 wins, 1 draw, 1 loss against experienced players. Using their current ratings, that would be about 1600, 1740, 1340, 1620, 1140. That would be an average of about 1380.

Hmm, can I have my rating recalculated? 🙄

This seems like a sensible change. Thanks Chris


-trekkie

Most of the sites I play at have provisional ratings for new players and its good that this is being worked on, but look at misterx and that players rating. After completing 1 game and winning against a 1480 players that players rating is almost 1900. I'm no mathematician but this seems a little high.

1800 may be a little high after one game. But that may be just where that player should be. It seems to make sense to me for a provisional player to possibly be there after one game.

Either he belongs in there somewhere and will end up there on his 21st game. Or he doesn't belong near there and by the time he starts his 21st game (thereby no longer a provisional player), he will be ranked appropriately where he should be (maybe lower, maybe higher). I'm not saying I think the formula is correct (I really haven't looked at the math of it), I'm just saying that a provisional score of 1800 after 1 game seems plausible. Now if there were LOTS of provisional scores in that area, I'd be suspicious of the formula.

I think if you see a provisional score near you in the rankings, you can either ignore the player (just provisional, will probably shift around anyway), or take it as notice that there's a new player with potentially similar skills as you. If you want to send that person down again, challenge 'em! 😏

Ogey

I feel the provisionally ranked players should have a different player table entries. 2 provisionally ranked players have gained entry in the top 20 list. Players ranked 21 & 22 may feel unhappy not to appear in the top 20 list.

Prashant has made a good point, but I don't think it's necessary. Well done 😀

Originally posted by Chrismo
This thread highlights some problems with the current rating system which I am about to address.

http://www.redhotpawn.com/board/showthread.php?id=575

The key point is that new joiners to the site need some time to 'find their level'. Also, established members currently have good reason to avoid playing new members because it may reflect inaccuratel ...[text shortened]... ent has played fewer than 20 games, then PA = 0.5, otherwise PA = 1

All thoughts welcome...

Ok but what about the player who beats someone whose won one game and got a high rating? Is that not fair that their rating shoots up after beating someone who isn't really ie a 1800 rated player. 😞

Originally posted by Serendipity
Ok but what about the player who beats someone whose won one game and got a high rating? Is that not fair that their rating shoots up after beating someone who isn't really ie a 1800 rated player. 😞

If someone's played less than 5 games, then their rating is regarded as being 1200. So a player who beats this person will not gain any more than beating an ordinary 1200 rated person. In fact, because the rating is provisional, the winner will only receive half the points he/she would normally gain from winning.

Let me give an example:-

Player A, who has recently joined the site, has completed 3 games - beating a 1400 opponent, a 1500, and a 1600. His provisional rating will be the average of 1400 + 400, 1500 + 400, 1600 + 400 = 1900.

Player B, who has played more than 20 rated games, is rated at 1650.

Player B challenges Player A and beats him.

Now Player B might be expecting to gain a great deal from beating a 1900 opponent, someone rated 250 points above him. But for rating purposes, Player A is regarded as being 1200, and a 1650 player should be able to beat a 1200 player in practically every game. Therefore he will gain practically nothing from the win. Player A's provisional rating will fall considerably, but Player B's rating will stay the same.

So my advice for anyone rated above 1200, is don’t expect to gain much, or anything at all, from playing someone who’s not yet completed 5 games.

Dave

Originally posted by Chrismo
...
K = 32, unless your rating > 2100, then K = 24, unless your rating > 2400, then K = 16
...
All thoughts welcome...

why do you make the function noncontinous?
th