Initial rating - Revision history

Dallasjohnson: /* Summary */

2014-06-08T15:50:57Z

‎Summary

Poslfit: /* Summary */ reworded more carefully to avoid contradictiion

2014-06-07T13:32:08Z

‎Summary: reworded more carefully to avoid contradictiion

Poslfit: updated for rating system changes 2011-09-21

2011-09-21T16:15:50Z

updated for rating system changes 2011-09-21

Poslfit: added three more explanations

2010-03-14T22:46:51Z

added three more explanations

Poslfit: New page: Here is how ratings are computed for newcomers (players who do not have a previous rating) at a tournament. Questions should be directed to John Chew. *'''For each''' rated player ''r...

2010-03-14T18:41:57Z

New page: Here is how ratings are computed for newcomers (players who do not have a previous rating) at a tournament. Questions should be directed to John Chew. *'''For each''' rated player ''r...

New page

Here is how ratings are computed for newcomers (players who do not
have a previous rating) at a tournament. Questions should
be directed to [[John Chew]].

*'''For each''' rated player ''rp''
**'''Set''' the ''iterative rating'' for ''rp'' to their ''pre-event rating''
*'''For each''' newcomer ''nc''
**'''Set''' the ''iterative rating'' for ''nc'' to the mean of their rated opponent ''ratings'', if any, else 1500
**'''Set''' ''nc''’s ''earned wins'' to the number of games won by ''nc'' at this event not including byes or forfeits
**'''Set''' ''nc''’s ''rated games'' to the number of games played by ''nc'' at this event not including byes or forfeits
**'''Define''' a '''function''' ''IPR<sub>nc</sub>''(''r'') as follows
***'''Set''' ''earned_wins'' = ''nc''’s ''earned wins''
***'''If''' ''earned_wins'' = 0
****'''then''' '''Set''' ''earned_wins'' to 5% * ''nc''’s ''rated games''
***'''else''' '''if''' ''earned_wins'' = ''rated_games''
****'''then''' '''Set''' ''earned_wins'' to 95% * ''nc''’s ''rated games''
***'''Set''' ''excess_wins'' = (sum of expected wins of a player rated ''r'' vs. opponents whose ratings are the ''iterative ratings'' of the opponents of ''nc'') - ''earned_wins''
***'''Return''' ''excess_wins''
*'''Repeat''' 50 times
**'''For each''' newcomer ''nc''
***Perform a binary search for an integer value ''r'' in [0,3000] stopping when the search range is less than or equal to one, setting the low (high) end of the range equal to the floor of the middle of the range when ''IPR<sub>nc</sub>''(''r'') is <0 (≥0)
***'''If''' ''r'' < 500
****'''then''' '''Set''' ''r'' to 500
***'''If''' ''nc'' has played a rated opponent
****'''then'''
*****'''Set''' ''maximum_rating'' to (greatest ''pre-event rating'' among ''nc''’s rated opponents) + 400 * ''nc''’s ''earned wins'' / ''nc''’s ''rated games''
*****if ''r'' > ''maximum_rating''
******'''then''' '''Set''' ''r to ''maximum_rating''
***'''Set''' ''nc''’s ''next rating'' to ''r''
**'''For each''' newcomer ''nc''
***'''Set''' ''nc''’s ''iterative rating'' to ''nc''’s ''next rating''
**'''If''' all ''iterative rating''s were equal to ''next rating''s
***'''then''' stop repeating now without continuing to the 50th iteration
*'''If''' fewer than 50 iterations were required
**'''For each''' newcomer ''nc''
***'''Set''' ''nc''’s new rating to ''nc''’s ''iterative rating''
*'''Else'''
**Perform 50 more iterations
**'''For each''' newcomer ''nc''
***'''Set''' ''nc''’s ''new rating'' to the mean of ''nc''’s last 50 ''iterative ratings''

@@ Line 18: / Line 18: @@
 the event in order for it to have remained
 unchanged), except that if their initial rating would be less than 500, it is raised to 500,
-and if it would the newcomer&rsquo;s strongest opponent&rsquo;s
+and if it would exceed the newcomer&rsquo;s strongest opponent&rsquo;s
 rating by more than 400 times the newcomer&rsquo;s
 winning percentage, it is decreased until it does not.

@@ Line 17: / Line 17: @@
 the newcomer would have had to have had before
 the event in order for it to have remained
-unchanged), except that an initial rating may
+unchanged), except that if their initial rating would be less than 500, it is raised to 500,
-never be less than 500, and it may
+and if it would the newcomer&rsquo;s strongest opponent&rsquo;s
 rating by more than 400 times the newcomer&rsquo;s
-winning percentage.
+winning percentage, it is decreased until it does not.
 If there is more than one newcomer, then they are

@@ Line 50: / Line 50: @@
 ***'''If''' ''r'' < 500
 ****'''then'''  '''Set''' ''r'' to 500
-***'''If''' ''nc'' has played a rated opponent
+***'''Set''' ''maximum_rating'' to (greatest among ''pre-event rating'' of ''nc''&rsquo;s rated opponents or ''iterative rating'' of ''nc''&rsquo;s unrated opponents) + 400 * ''nc''&rsquo;s ''earned wins'' / ''nc''&rsquo;s ''rated games''
-****'''then'''
+***if ''r'' > ''maximum_rating''
-*****'''Set''' ''maximum_rating'' to (greatest ''pre-event rating'' among ''nc''&rsquo;s rated opponents) + 400 * ''nc''&rsquo;s ''earned wins'' / ''nc''&rsquo;s ''rated games''
+****'''then'''  '''Set''' ''r to ''maximum_rating''
 ***'''Set''' ''nc''&rsquo;s ''next rating'' to ''r''
 **'''For each''' newcomer ''nc''

@@ Line 1: / Line 1: @@
-Here is how ratings are computed for newcomers (players who do not
+Here are four explanations of how ratings are computed for newcomers (players who do not
-have a previous rating) at a tournament. Questions should
+have a previous rating) at a tournament,
 be directed to [[John Chew]].
 *'''For each''' rated player ''rp''
@@ Line 39: / Line 67: @@
 **'''For each''' newcomer ''nc''
 ***'''Set''' ''nc''&rsquo;s ''new rating'' to the mean of ''nc''&rsquo;s last 50 ''iterative ratings''