{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2026-04-06T14:01:22.000Z","description":"Problems submitted by members of the MATLAB Central community.","is_default":true,"created_by":161519,"badge_id":null,"featured":false,"trending":false,"solution_count_in_trending_period":0,"trending_last_calculated":"2026-04-06T00:00:00.000Z","image_id":null,"published":true,"community_created":false,"status_id":2,"is_default_group_for_player":false,"deleted_by":null,"deleted_at":null,"restored_by":null,"restored_at":null,"description_opc":null,"description_html":null,"published_at":null},"problems":[{"id":3054,"title":"Chess ELO rating system","description":"The Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. ( \u003chttp://en.wikipedia.org/wiki/Elo_rating_system\u003e )\r\n\r\nThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\r\n\r\nSome chess organizations use the \"algorithm of 400\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\r\n\r\nFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.","description_html":"\u003cp\u003eThe Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. ( \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003ehttp://en.wikipedia.org/wiki/Elo_rating_system\u003c/a\u003e )\u003c/p\u003e\u003cp\u003eThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/p\u003e\u003cp\u003eSome chess organizations use the \"algorithm of 400\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\u003c/p\u003e\u003cp\u003eFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.\u003c/p\u003e","function_template":"function y = algo400(players,result)\r\n  y = x;\r\nend","test_suite":"%%\r\nplayers = 1000;\r\nresult = 1;\r\nassert(isequal(algo400(players,result),1400))\r\n%%\r\nplayers = 1000;\r\nresult = 0.5;\r\nassert(isequal(algo400(players,result),1000))\r\n%%\r\nassert(isequal(algo400([2000 2000],[0.5 0.5]),2000))\r\n%%\r\nplayers = [2000 2000];\r\nresult = [1 1];\r\nassert(isequal(algo400(players,result),2400))\r\n%%\r\nplayers = [2000 2000];\r\nresult = [0.5 1];\r\nassert(isequal(algo400(players,result),2200))\r\n%%\r\nplayers = [2000 2100 2200 2300];\r\nresult = [1 0.5 1 0.5];\r\nassert(isequal(algo400(players,result),2350))\r\n%%\r\nplayers = 1000;\r\nresult = 1;\r\nassert(isequal(algo400(players,result),1400))\r\n%% My last performance (my ELO is 1800)\r\nplayers = [1399 1280 2166 1534 1768 1791 1540];\r\nresult = [1 1 0 1 1 0 1];\r\nassert(isequal(round(algo400(players,result)),1811))\r\n%%\r\nplayers = [2000 2100 2200 2300];\r\nresult = [0.5 0.5 0.5 0.5];\r\nassert(isequal(algo400(players,result),2150))\r\n%% Caruana perfomance in 2014 Sinquefield Cup\r\nplayers = [2772 2768 2877 2805 2787  2772 2768 2877 2787 2805];\r\nresult = [1 1 1 1 1 1 1 0.5 0.5 0.5];\r\nassert(isequal(round(algo400(players,result)),3082))\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":1,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":96,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T18:02:19.000Z","updated_at":"2026-02-15T07:29:20.000Z","published_at":"2015-02-28T18:03:21.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. (\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehttp://en.wikipedia.org/wiki/Elo_rating_system\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e )\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSome chess organizations use the \\\"algorithm of 400\\\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":3057,"title":"Chess performance","description":"After Problems \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/ 3054\u003e and \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/ 3056\u003e\r\n\r\n\r\nIn \u003chttp://en.wikipedia.org/wiki/Elo_rating_system Chess\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\r\n\r\nSupposing Player A was expected to score Ea points (but actually scored Sa).\r\n\r\nThe formula for updating his rating is :\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/2/3/f/23fbcb658ac1e2565003c2190f28a21e.png\u003e\u003e\r\n\r\n* \r\n* \r\n\r\n\r\nThis update can be performed after each game or each tournament, or after any suitable rating period. \r\n\r\nSuppose Player A has a rating *Ra* of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score *Sa* is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score *Ea* , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating *R'a* is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the *K* factor is always 32.\r\n\r\nI give you rating of Player A, ratings of their opponents and results. \r\n\r\nCompute the new rating (K = 32).\r\n\r\n\r\n","description_html":"\u003cp\u003eAfter Problems \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/\"\u003e3054\u003c/a\u003e and \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\"\u003e3056\u003c/a\u003e\u003c/p\u003e\u003cp\u003eIn \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003eChess\u003c/a\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\u003c/p\u003e\u003cp\u003eSupposing Player A was expected to score Ea points (but actually scored Sa).\u003c/p\u003e\u003cp\u003eThe formula for updating his rating is :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/2/3/f/23fbcb658ac1e2565003c2190f28a21e.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eThis update can be performed after each game or each tournament, or after any suitable rating period.\u003c/p\u003e\u003cp\u003eSuppose Player A has a rating \u003cb\u003eRa\u003c/b\u003e of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score \u003cb\u003eSa\u003c/b\u003e is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score \u003cb\u003eEa\u003c/b\u003e , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating \u003cb\u003eR'a\u003c/b\u003e is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the \u003cb\u003eK\u003c/b\u003e factor is always 32.\u003c/p\u003e\u003cp\u003eI give you rating of Player A, ratings of their opponents and results.\u003c/p\u003e\u003cp\u003eCompute the new rating (K = 32).\u003c/p\u003e","function_template":"function y = new_elo(opponents_elo,res,elo_playerA)\r\n  y = x;\r\nend","test_suite":"%%\r\nplayera=1613;\r\nelos=[1609 1477 1388 1586 1720];\r\nres=[0 0.5 1 1 0];\r\nassert(isequal(new_elo(elos,res,playera),1601))\r\n%%\r\nplayera=1613;\r\nelos=[1609 1477 1586 1720];\r\nres=[0 1 1 1];\r\nassert(isequal(new_elo(elos,res,playera),1642))\r\n%%\r\nplayera=1613;\r\nelos=[1613 1613 1613 1613 1613];\r\nres=[0.5 0.5 0.5 0.5 0.5];\r\nassert(isequal(new_elo(elos,res,playera),1613))\r\n%%\r\nassert(isequal(new_elo([1800 1900 2000 2100 2200],[1 0 1 0 1],1900),1935))\r\n%% My new ELO\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 0 1 1 0 1];\r\nassert(isequal(new_elo(elos,res,playera),1811))\r\n%% The last game was critical (-32 points if I lost)\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 0 1 1 0 0];\r\nassert(isequal(new_elo(elos,res,playera),1779))\r\n%% Perfect tournament ?\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 1 1 1 1 1];\r\nassert(isequal(new_elo(elos,res,playera),1875))\r\n%% Caruana in 2014 Sinquefield Cup (notice that K=16 for these guys)\r\ncaruana=2801;\r\nelos = [2772 2768 2877 2805 2787  2772 2768 2877 2787 2805];\r\nres = [1 1 1 1 1 1 1 0.5 0.5 0.5];\r\nassert(isequal(new_elo(elos,res,caruana),2913))","published":true,"deleted":false,"likes_count":3,"comments_count":5,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":65,"test_suite_updated_at":"2015-03-02T20:49:24.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T23:49:25.000Z","updated_at":"2026-02-15T07:24:43.000Z","published_at":"2015-02-28T23:53:01.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAfter Problems\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3054\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3056\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eChess\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSupposing Player A was expected to score Ea points (but actually scored Sa).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe formula for updating his rating is :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis update can be performed after each game or each tournament, or after any suitable rating period.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSuppose Player A has a rating\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eRa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eSa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eEa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eR'a\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eK\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e factor is always 32.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you rating of Player A, ratings of their opponents and results.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eCompute the new rating (K = 32).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"},{\"partUri\":\"/media/image1.png\",\"contentType\":\"image/png\",\"content\":\"data:image/png;base64,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\"}]}"},{"id":3056,"title":"Chess probability","description":"The difference in the ratings between two players serves as a predictor of the outcome of a match (the \u003chttp://en.wikipedia.org/wiki/Elo_rating_system Elo rating system\u003e)\r\n\r\nIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\u003e\u003e\r\n \r\n* \r\n \r\n\r\nTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\r\n\r\nI give you two ELOs, compute the expected score (round to 3 digits), or probability  that the first player wins.\r\n\r\n\r\n","description_html":"\u003cp\u003eThe difference in the ratings between two players serves as a predictor of the outcome of a match (the \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003eElo rating system\u003c/a\u003e)\u003c/p\u003e\u003cp\u003eIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/p\u003e\u003cp\u003eI give you two ELOs, compute the expected score (round to 3 digits), or probability  that the first player wins.\u003c/p\u003e","function_template":"function y = expected_score(elo1,elo2)\r\n  y = x;\r\nend","test_suite":"%%\r\nx = 1800;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.5))\r\n%%\r\nx = 1900;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.64))\r\n%%\r\nx = 1900;\r\ny = 2000;\r\nassert(isequal(expected_score(x,y),0.36))\r\n%%\r\nx = 1900;\r\ny = 2100;\r\nassert(isequal(expected_score(x,y),0.24))\r\n%% My probability against Maxime Vachier-Lagrave (best french player)\r\nx = 1800;\r\ny = 2775;\r\nassert(isequal(expected_score(x,y),0.004))\r\n%% My probability against Magnus Carlsen (World Chess Champion)\r\nx = 1800;\r\ny = 2865;\r\nassert(isequal(expected_score(x,y),0.002))\r\n%% Magnus against Maxime\r\nx = 2865;\r\ny = 2775;\r\nassert(isequal(expected_score(x,y),0.627))\r\n%% Magnus Carlsen against Garry Kasparov (1999)\r\nx = 2865;\r\ny = 2851;\r\nassert(isequal(expected_score(x,y),0.52))\r\n%% Magnus Carlsen against Fabiano Caruana\r\nx = 2865;\r\ny = 2844;\r\nassert(isequal(expected_score(x,y),0.53))\r\n%% Bobby Fisher (1972) against Magnus Carlsen\r\nx = 2785;\r\ny = 2865;\r\nassert(isequal(expected_score(x,y),0.387))\r\n%% Bobby Fisher (1972) against me\r\nx = 2785;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.997))\r\n","published":true,"deleted":false,"likes_count":6,"comments_count":0,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":681,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T22:51:09.000Z","updated_at":"2026-04-06T20:34:45.000Z","published_at":"2015-02-28T22:52:00.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe difference in the ratings between two players serves as a predictor of the outcome of a match (the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eElo rating system\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e)\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you two ELOs, compute the expected score (round to 3 digits), or probability that the first player wins.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"},{\"partUri\":\"/media/image1.png\",\"contentType\":\"image/png\",\"content\":\"data:image/png;base64,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\"}]}"},{"id":3061,"title":"Mirror, mirror on the wall, who is fairest of them all?","description":"The Elo rating system was featured in the movie *The Social Network* during the \u003chttps://www.youtube.com/watch?v=BzZRr4KV59I/ algorithm scene\u003e where Mark Zuckerberg released Facemash. \r\n\r\nIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. \r\nThe Elo system is employed to rank coeds by their attractiveness. \r\nThe equations driving the algorithm are shown briefly (Ea and Eb). \r\n\r\nYou should know these equations now (See problem \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/ 3056\u003e) :\r\n\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\u003e\u003e\r\n \r\n* \r\n\r\n\r\nEa is the expected probability that Girl A will win the match against Girl B.\r\n\r\nRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\r\n\r\nNow imagine a single round-robin tournament where each girl plays (is compared with)  every other girl once.\r\nA judge (me for the problem) gives a note :\r\n\r\n* 1   if girl A is more attractive than girl B\r\n* 0   if girl B is more attractive than girl A\r\n* 0.5 if same attractiveness\r\n\r\nI give you the tournament results (2 on the main diagonal).\r\n\r\nFind the final rating of Snow White (she is unique).\r\n\r\nConsider that all girl begin the tournament with a rating of 1000.\r\n\r\nYou can observe that the total number of attractiveness (ELO) points remains constant.\r\n","description_html":"\u003cp\u003eThe Elo rating system was featured in the movie \u003cb\u003eThe Social Network\u003c/b\u003e during the \u003ca href = \"https://www.youtube.com/watch?v=BzZRr4KV59I/\"\u003ealgorithm scene\u003c/a\u003e where Mark Zuckerberg released Facemash.\u003c/p\u003e\u003cp\u003eIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. \r\nThe Elo system is employed to rank coeds by their attractiveness. \r\nThe equations driving the algorithm are shown briefly (Ea and Eb).\u003c/p\u003e\u003cp\u003eYou should know these equations now (See problem \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\"\u003e3056\u003c/a\u003e) :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eEa is the expected probability that Girl A will win the match against Girl B.\u003c/p\u003e\u003cp\u003eRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\u003c/p\u003e\u003cp\u003eNow imagine a single round-robin tournament where each girl plays (is compared with)  every other girl once.\r\nA judge (me for the problem) gives a note :\u003c/p\u003e\u003cul\u003e\u003cli\u003e1   if girl A is more attractive than girl B\u003c/li\u003e\u003cli\u003e0   if girl B is more attractive than girl A\u003c/li\u003e\u003cli\u003e0.5 if same attractiveness\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eI give you the tournament results (2 on the main diagonal).\u003c/p\u003e\u003cp\u003eFind the final rating of Snow White (she is unique).\u003c/p\u003e\u003cp\u003eConsider that all girl begin the tournament with a rating of 1000.\u003c/p\u003e\u003cp\u003eYou can observe that the total number of attractiveness (ELO) points remains constant.\u003c/p\u003e","function_template":"function y = fairest_girl(X)\r\n  y = X;\r\nend","test_suite":"%%\r\nA=[2 1 1 1 1;0 2 1 1 1;0 0 2 1 1;0 0 0 2 1;0 0 0 0 2];\r\nassert(isequal(fairest_girl(A),1064));\r\n%%\r\nA=[2 1;0 2];\r\nassert(isequal(fairest_girl(A),1016));\r\n%%\r\nassert(isequal(fairest_girl([2 1 0.5;0 2 0.5;0.5 0.5 2]),1016));\r\n%%\r\nA=[2 1 1 1 1 1;0 2 1 1 1 1;0 0 2 1 1 1;0 0 0 2 0.5 0.5;0 0 0 0.5 2 0.5;0 0 0 0.5 0.5 2];\r\nassert(isequal(fairest_girl(A),1080));\r\n%%\r\nA=[2 0.5 1;0.5 2 0.5;0 0.5 2];\r\nassert(isequal(fairest_girl(A),1016));\r\n%%\r\nA=[2 1 1 1 1 1 1;0 2 1 1 1 1 1;0 0 2 1 1 1 1;0 0 0 2 0.5 0.5 1;0 0 0 0.5 2 0.5 1;0 0 0 0.5 0.5 2 1;0 0 0 0 0 0 2];\r\nassert(isequal(fairest_girl(A),1096));\r\n%%\r\nA=[2 1 1 1 1 1 0.5;0 2 1 1 1 1 0.5;0 0 2 1 1 1 0.5;0 0 0 2 0.5 0.5 0.5;0 0 0 0.5 2 0.5 0.5;0 0 0 0.5 0.5 2 0.5;0.5 0.5 0.5 0.5 0.5 0.5 2];\r\nassert(isequal(fairest_girl(A),1080));\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":1,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":18,"test_suite_updated_at":"2015-03-03T18:22:50.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2015-03-03T18:06:46.000Z","updated_at":"2026-04-01T09:44:49.000Z","published_at":"2015-03-03T18:13:07.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Elo rating system was featured in the movie\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eThe Social Network\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e during the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"https://www.youtube.com/watch?v=BzZRr4KV59I/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ealgorithm scene\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e where Mark Zuckerberg released Facemash.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. The Elo system is employed to rank coeds by their attractiveness. The equations driving the algorithm are shown briefly (Ea and Eb).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou should know these equations now (See problem\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3056\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e) :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eEa is the expected probability that Girl A will win the match against Girl B.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eNow imagine a single round-robin tournament where each girl plays (is compared with) every other girl once. A judge (me for the problem) gives a note :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e1 if girl A is more attractive than girl B\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e0 if girl B is more attractive than girl A\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e0.5 if same attractiveness\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you the tournament results (2 on the main diagonal).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind the final rating of Snow White (she is unique).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eConsider that all girl begin the tournament with a rating of 1000.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou can observe that the total number of attractiveness (ELO) points remains constant.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"},{\"partUri\":\"/media/image1.png\",\"contentType\":\"image/png\",\"content\":\"data:image/png;base64,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\"}]}"}],"problem_search":{"errors":[],"problems":[{"id":3054,"title":"Chess ELO rating system","description":"The Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. ( \u003chttp://en.wikipedia.org/wiki/Elo_rating_system\u003e )\r\n\r\nThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\r\n\r\nSome chess organizations use the \"algorithm of 400\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\r\n\r\nFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.","description_html":"\u003cp\u003eThe Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. ( \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003ehttp://en.wikipedia.org/wiki/Elo_rating_system\u003c/a\u003e )\u003c/p\u003e\u003cp\u003eThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/p\u003e\u003cp\u003eSome chess organizations use the \"algorithm of 400\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\u003c/p\u003e\u003cp\u003eFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.\u003c/p\u003e","function_template":"function y = algo400(players,result)\r\n  y = x;\r\nend","test_suite":"%%\r\nplayers = 1000;\r\nresult = 1;\r\nassert(isequal(algo400(players,result),1400))\r\n%%\r\nplayers = 1000;\r\nresult = 0.5;\r\nassert(isequal(algo400(players,result),1000))\r\n%%\r\nassert(isequal(algo400([2000 2000],[0.5 0.5]),2000))\r\n%%\r\nplayers = [2000 2000];\r\nresult = [1 1];\r\nassert(isequal(algo400(players,result),2400))\r\n%%\r\nplayers = [2000 2000];\r\nresult = [0.5 1];\r\nassert(isequal(algo400(players,result),2200))\r\n%%\r\nplayers = [2000 2100 2200 2300];\r\nresult = [1 0.5 1 0.5];\r\nassert(isequal(algo400(players,result),2350))\r\n%%\r\nplayers = 1000;\r\nresult = 1;\r\nassert(isequal(algo400(players,result),1400))\r\n%% My last performance (my ELO is 1800)\r\nplayers = [1399 1280 2166 1534 1768 1791 1540];\r\nresult = [1 1 0 1 1 0 1];\r\nassert(isequal(round(algo400(players,result)),1811))\r\n%%\r\nplayers = [2000 2100 2200 2300];\r\nresult = [0.5 0.5 0.5 0.5];\r\nassert(isequal(algo400(players,result),2150))\r\n%% Caruana perfomance in 2014 Sinquefield Cup\r\nplayers = [2772 2768 2877 2805 2787  2772 2768 2877 2787 2805];\r\nresult = [1 1 1 1 1 1 1 0.5 0.5 0.5];\r\nassert(isequal(round(algo400(players,result)),3082))\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":1,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":96,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T18:02:19.000Z","updated_at":"2026-02-15T07:29:20.000Z","published_at":"2015-02-28T18:03:21.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Elo rating system is a method for calculating the relative chess skill levels of players in competitor-versus-competitor games. (\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehttp://en.wikipedia.org/wiki/Elo_rating_system\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e )\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe difference in the ratings (rating=ELO) between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSome chess organizations use the \\\"algorithm of 400\\\" to calculate performance rating. According to this algorithm, performance rating for an event is calculated by taking (1) the rating of each player beaten and adding 400, (2) the rating of each player lost to and subtracting 400, (3) the rating of each player drawn, and (4) summing these figures and dividing by the number of games played.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind the performance with this algorithm with ELO players and results (0=loss,0.5=draw,1=win) in input.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":3057,"title":"Chess performance","description":"After Problems \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/ 3054\u003e and \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/ 3056\u003e\r\n\r\n\r\nIn \u003chttp://en.wikipedia.org/wiki/Elo_rating_system Chess\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\r\n\r\nSupposing Player A was expected to score Ea points (but actually scored Sa).\r\n\r\nThe formula for updating his rating is :\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/2/3/f/23fbcb658ac1e2565003c2190f28a21e.png\u003e\u003e\r\n\r\n* \r\n* \r\n\r\n\r\nThis update can be performed after each game or each tournament, or after any suitable rating period. \r\n\r\nSuppose Player A has a rating *Ra* of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score *Sa* is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score *Ea* , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating *R'a* is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the *K* factor is always 32.\r\n\r\nI give you rating of Player A, ratings of their opponents and results. \r\n\r\nCompute the new rating (K = 32).\r\n\r\n\r\n","description_html":"\u003cp\u003eAfter Problems \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/\"\u003e3054\u003c/a\u003e and \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\"\u003e3056\u003c/a\u003e\u003c/p\u003e\u003cp\u003eIn \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003eChess\u003c/a\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\u003c/p\u003e\u003cp\u003eSupposing Player A was expected to score Ea points (but actually scored Sa).\u003c/p\u003e\u003cp\u003eThe formula for updating his rating is :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/2/3/f/23fbcb658ac1e2565003c2190f28a21e.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eThis update can be performed after each game or each tournament, or after any suitable rating period.\u003c/p\u003e\u003cp\u003eSuppose Player A has a rating \u003cb\u003eRa\u003c/b\u003e of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score \u003cb\u003eSa\u003c/b\u003e is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score \u003cb\u003eEa\u003c/b\u003e , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating \u003cb\u003eR'a\u003c/b\u003e is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the \u003cb\u003eK\u003c/b\u003e factor is always 32.\u003c/p\u003e\u003cp\u003eI give you rating of Player A, ratings of their opponents and results.\u003c/p\u003e\u003cp\u003eCompute the new rating (K = 32).\u003c/p\u003e","function_template":"function y = new_elo(opponents_elo,res,elo_playerA)\r\n  y = x;\r\nend","test_suite":"%%\r\nplayera=1613;\r\nelos=[1609 1477 1388 1586 1720];\r\nres=[0 0.5 1 1 0];\r\nassert(isequal(new_elo(elos,res,playera),1601))\r\n%%\r\nplayera=1613;\r\nelos=[1609 1477 1586 1720];\r\nres=[0 1 1 1];\r\nassert(isequal(new_elo(elos,res,playera),1642))\r\n%%\r\nplayera=1613;\r\nelos=[1613 1613 1613 1613 1613];\r\nres=[0.5 0.5 0.5 0.5 0.5];\r\nassert(isequal(new_elo(elos,res,playera),1613))\r\n%%\r\nassert(isequal(new_elo([1800 1900 2000 2100 2200],[1 0 1 0 1],1900),1935))\r\n%% My new ELO\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 0 1 1 0 1];\r\nassert(isequal(new_elo(elos,res,playera),1811))\r\n%% The last game was critical (-32 points if I lost)\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 0 1 1 0 0];\r\nassert(isequal(new_elo(elos,res,playera),1779))\r\n%% Perfect tournament ?\r\nplayera=1800;\r\nelos=[1399 1280 2166 1534 1768 1791 1540];\r\nres=[1 1 1 1 1 1 1];\r\nassert(isequal(new_elo(elos,res,playera),1875))\r\n%% Caruana in 2014 Sinquefield Cup (notice that K=16 for these guys)\r\ncaruana=2801;\r\nelos = [2772 2768 2877 2805 2787  2772 2768 2877 2787 2805];\r\nres = [1 1 1 1 1 1 1 0.5 0.5 0.5];\r\nassert(isequal(new_elo(elos,res,caruana),2913))","published":true,"deleted":false,"likes_count":3,"comments_count":5,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":65,"test_suite_updated_at":"2015-03-02T20:49:24.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T23:49:25.000Z","updated_at":"2026-02-15T07:24:43.000Z","published_at":"2015-02-28T23:53:01.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAfter Problems\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3054-chess-elo-rating-system/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3054\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3056\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eChess\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e, performance isn't measured absolutely; it is inferred from wins (1), losses (0), and draws (0.5) against other players. A player's rating depends on the ratings of their opponents, and the results scored against them. The difference in rating between two players determines an estimate for the expected score between them.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSupposing Player A was expected to score Ea points (but actually scored Sa).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe formula for updating his rating is :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis update can be performed after each game or each tournament, or after any suitable rating period.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSuppose Player A has a rating\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eRa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e of 1613, and plays in a five-round tournament. He (or she) loses to a player rated 1609, draws with a player rated 1477, defeats a player rated 1388, defeats a player rated 1586, and loses to a player rated 1720. The player's actual score\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eSa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e is (0 + 0.5 + 1 + 1 + 0) = 2.5. The expected score\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eEa\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e , calculated according to the formula see in Problem 3056, was (0.506 + 0.686 + 0.785 + 0.539 + 0.351) = 2.867. Therefore the player's new rating\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eR'a\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e is (1613 + 32×(2.5 − 2.867)) = 1601. We assume that the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eK\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e factor is always 32.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you rating of Player A, ratings of their opponents and results.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eCompute the new rating (K = 32).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"},{\"partUri\":\"/media/image1.png\",\"contentType\":\"image/png\",\"content\":\"data:image/png;base64,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\"}]}"},{"id":3056,"title":"Chess probability","description":"The difference in the ratings between two players serves as a predictor of the outcome of a match (the \u003chttp://en.wikipedia.org/wiki/Elo_rating_system Elo rating system\u003e)\r\n\r\nIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\u003e\u003e\r\n \r\n* \r\n \r\n\r\nTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\r\n\r\nI give you two ELOs, compute the expected score (round to 3 digits), or probability  that the first player wins.\r\n\r\n\r\n","description_html":"\u003cp\u003eThe difference in the ratings between two players serves as a predictor of the outcome of a match (the \u003ca href = \"http://en.wikipedia.org/wiki/Elo_rating_system\"\u003eElo rating system\u003c/a\u003e)\u003c/p\u003e\u003cp\u003eIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/p\u003e\u003cp\u003eI give you two ELOs, compute the expected score (round to 3 digits), or probability  that the first player wins.\u003c/p\u003e","function_template":"function y = expected_score(elo1,elo2)\r\n  y = x;\r\nend","test_suite":"%%\r\nx = 1800;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.5))\r\n%%\r\nx = 1900;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.64))\r\n%%\r\nx = 1900;\r\ny = 2000;\r\nassert(isequal(expected_score(x,y),0.36))\r\n%%\r\nx = 1900;\r\ny = 2100;\r\nassert(isequal(expected_score(x,y),0.24))\r\n%% My probability against Maxime Vachier-Lagrave (best french player)\r\nx = 1800;\r\ny = 2775;\r\nassert(isequal(expected_score(x,y),0.004))\r\n%% My probability against Magnus Carlsen (World Chess Champion)\r\nx = 1800;\r\ny = 2865;\r\nassert(isequal(expected_score(x,y),0.002))\r\n%% Magnus against Maxime\r\nx = 2865;\r\ny = 2775;\r\nassert(isequal(expected_score(x,y),0.627))\r\n%% Magnus Carlsen against Garry Kasparov (1999)\r\nx = 2865;\r\ny = 2851;\r\nassert(isequal(expected_score(x,y),0.52))\r\n%% Magnus Carlsen against Fabiano Caruana\r\nx = 2865;\r\ny = 2844;\r\nassert(isequal(expected_score(x,y),0.53))\r\n%% Bobby Fisher (1972) against Magnus Carlsen\r\nx = 2785;\r\ny = 2865;\r\nassert(isequal(expected_score(x,y),0.387))\r\n%% Bobby Fisher (1972) against me\r\nx = 2785;\r\ny = 1800;\r\nassert(isequal(expected_score(x,y),0.997))\r\n","published":true,"deleted":false,"likes_count":6,"comments_count":0,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":681,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-02-28T22:51:09.000Z","updated_at":"2026-04-06T20:34:45.000Z","published_at":"2015-02-28T22:52:00.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe difference in the ratings between two players serves as a predictor of the outcome of a match (the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://en.wikipedia.org/wiki/Elo_rating_system\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eElo rating system\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e)\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf Player A has a rating of Ra and Player B a rating of Rb, the formula for the expected score of Player A is :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eTwo players with equal ratings who play against each other are expected to score an equal number of wins. A player whose rating is 100 points greater than their opponent's is expected to score 64%; if the difference is 200 points, then the expected score for the stronger player is 76%.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you two ELOs, compute the expected score (round to 3 digits), or probability that the first player wins.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"},{\"partUri\":\"/media/image1.png\",\"contentType\":\"image/png\",\"content\":\"data:image/png;base64,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\"}]}"},{"id":3061,"title":"Mirror, mirror on the wall, who is fairest of them all?","description":"The Elo rating system was featured in the movie *The Social Network* during the \u003chttps://www.youtube.com/watch?v=BzZRr4KV59I/ algorithm scene\u003e where Mark Zuckerberg released Facemash. \r\n\r\nIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. \r\nThe Elo system is employed to rank coeds by their attractiveness. \r\nThe equations driving the algorithm are shown briefly (Ea and Eb). \r\n\r\nYou should know these equations now (See problem \u003chttp://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/ 3056\u003e) :\r\n\r\n\r\n\u003c\u003chttp://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\u003e\u003e\r\n \r\n* \r\n\r\n\r\nEa is the expected probability that Girl A will win the match against Girl B.\r\n\r\nRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\r\n\r\nNow imagine a single round-robin tournament where each girl plays (is compared with)  every other girl once.\r\nA judge (me for the problem) gives a note :\r\n\r\n* 1   if girl A is more attractive than girl B\r\n* 0   if girl B is more attractive than girl A\r\n* 0.5 if same attractiveness\r\n\r\nI give you the tournament results (2 on the main diagonal).\r\n\r\nFind the final rating of Snow White (she is unique).\r\n\r\nConsider that all girl begin the tournament with a rating of 1000.\r\n\r\nYou can observe that the total number of attractiveness (ELO) points remains constant.\r\n","description_html":"\u003cp\u003eThe Elo rating system was featured in the movie \u003cb\u003eThe Social Network\u003c/b\u003e during the \u003ca href = \"https://www.youtube.com/watch?v=BzZRr4KV59I/\"\u003ealgorithm scene\u003c/a\u003e where Mark Zuckerberg released Facemash.\u003c/p\u003e\u003cp\u003eIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. \r\nThe Elo system is employed to rank coeds by their attractiveness. \r\nThe equations driving the algorithm are shown briefly (Ea and Eb).\u003c/p\u003e\u003cp\u003eYou should know these equations now (See problem \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\"\u003e3056\u003c/a\u003e) :\u003c/p\u003e\u003cimg src = \"http://upload.wikimedia.org/math/b/0/3/b0366725c224ee55eab6e2371dc6a0ef.png\"\u003e\u003cul\u003e\u003cli\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eEa is the expected probability that Girl A will win the match against Girl B.\u003c/p\u003e\u003cp\u003eRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\u003c/p\u003e\u003cp\u003eNow imagine a single round-robin tournament where each girl plays (is compared with)  every other girl once.\r\nA judge (me for the problem) gives a note :\u003c/p\u003e\u003cul\u003e\u003cli\u003e1   if girl A is more attractive than girl B\u003c/li\u003e\u003cli\u003e0   if girl B is more attractive than girl A\u003c/li\u003e\u003cli\u003e0.5 if same attractiveness\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eI give you the tournament results (2 on the main diagonal).\u003c/p\u003e\u003cp\u003eFind the final rating of Snow White (she is unique).\u003c/p\u003e\u003cp\u003eConsider that all girl begin the tournament with a rating of 1000.\u003c/p\u003e\u003cp\u003eYou can observe that the total number of attractiveness (ELO) points remains constant.\u003c/p\u003e","function_template":"function y = fairest_girl(X)\r\n  y = X;\r\nend","test_suite":"%%\r\nA=[2 1 1 1 1;0 2 1 1 1;0 0 2 1 1;0 0 0 2 1;0 0 0 0 2];\r\nassert(isequal(fairest_girl(A),1064));\r\n%%\r\nA=[2 1;0 2];\r\nassert(isequal(fairest_girl(A),1016));\r\n%%\r\nassert(isequal(fairest_girl([2 1 0.5;0 2 0.5;0.5 0.5 2]),1016));\r\n%%\r\nA=[2 1 1 1 1 1;0 2 1 1 1 1;0 0 2 1 1 1;0 0 0 2 0.5 0.5;0 0 0 0.5 2 0.5;0 0 0 0.5 0.5 2];\r\nassert(isequal(fairest_girl(A),1080));\r\n%%\r\nA=[2 0.5 1;0.5 2 0.5;0 0.5 2];\r\nassert(isequal(fairest_girl(A),1016));\r\n%%\r\nA=[2 1 1 1 1 1 1;0 2 1 1 1 1 1;0 0 2 1 1 1 1;0 0 0 2 0.5 0.5 1;0 0 0 0.5 2 0.5 1;0 0 0 0.5 0.5 2 1;0 0 0 0 0 0 2];\r\nassert(isequal(fairest_girl(A),1096));\r\n%%\r\nA=[2 1 1 1 1 1 0.5;0 2 1 1 1 1 0.5;0 0 2 1 1 1 0.5;0 0 0 2 0.5 0.5 0.5;0 0 0 0.5 2 0.5 0.5;0 0 0 0.5 0.5 2 0.5;0.5 0.5 0.5 0.5 0.5 0.5 2];\r\nassert(isequal(fairest_girl(A),1080));\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":1,"created_by":5390,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":18,"test_suite_updated_at":"2015-03-03T18:22:50.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2015-03-03T18:06:46.000Z","updated_at":"2026-04-01T09:44:49.000Z","published_at":"2015-03-03T18:13:07.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/image\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/media/image1.png\"}],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Elo rating system was featured in the movie\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eThe Social Network\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e during the\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"https://www.youtube.com/watch?v=BzZRr4KV59I/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ealgorithm scene\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e where Mark Zuckerberg released Facemash.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn the scene Eduardo Saverin writes mathematical formulas for the Elo rating system on Zuckerberg's dorm room window. The Elo system is employed to rank coeds by their attractiveness. The equations driving the algorithm are shown briefly (Ea and Eb).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou should know these equations now (See problem\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/3056-chess-probability/\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e3056\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e) :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:customXml w:element=\\\"image\\\"\u003e\u003cw:customXmlPr\u003e\u003cw:attr w:name=\\\"height\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"width\\\" w:val=\\\"-1\\\"/\u003e\u003cw:attr w:name=\\\"relationshipId\\\" w:val=\\\"rId1\\\"/\u003e\u003c/w:customXmlPr\u003e\u003c/w:customXml\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eEa is the expected probability that Girl A will win the match against Girl B.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRa is the rating of Girl A, which changes after tournament, according to the formula (Ra )n = (Ra )n-1 + 32 (W - Ea ) where W = {1,0.5,0}.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eNow imagine a single round-robin tournament where each girl plays (is compared with) every other girl once. A judge (me for the problem) gives a note :\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e1 if girl A is more attractive than girl B\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e0 if girl B is more attractive than girl A\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e0.5 if same attractiveness\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI give you the tournament results (2 on the main diagonal).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind the final rating of Snow White (she is unique).\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eConsider that all girl begin the tournament with a rating of 1000.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou can observe that the total number of attractiveness (ELO) points remains 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