Rankings

gistfile1.py

#!/usr/bin/env python

# -*- coding: utf-8 -*-
import operator
import pprint

matches = [
    { "h": {"name": "PG", "score": 2}, "a": {"name": "MK", "score": 2} },
    { "h": {"name": "PG", "score": 1}, "a": {"name": "MK", "score": 2} },
    { "h": {"name": "MK", "score": 1}, "a": {"name": "PG", "score": 0} },
    { "h": {"name": "GT", "score": 1}, "a": {"name": "MK", "score": 2} },
    { "h": {"name": "NP", "score": 2}, "a": {"name": "MK", "score": 1} },
    { "h": {"name": "PG", "score": 0}, "a": {"name": "MC", "score": 1} },
    { "h": {"name": "PG", "score": 0}, "a": {"name": "JH", "score": 0} },
    { "h": {"name": "PG", "score": 3}, "a": {"name": "CBo", "score": 0} },
    { "h": {"name": "PG", "score": 1}, "a": {"name": "NP", "score": 1} },
    { "h": {"name": "MC", "score": 1}, "a": {"name": "DG", "score": 2} },
    { "h": {"name": "MC", "score": 0}, "a": {"name": "DK", "score": 0} },
    { "h": {"name": "DK", "score": 3}, "a": {"name": "CBo", "score": 0} },
    { "h": {"name": "AB", "score": 0}, "a": {"name": "CBo", "score": 0} },
    { "h": {"name": "CBo", "score": 2}, "a": {"name": "JH", "score": 0} },
    { "h": {"name": "GT", "score": 1}, "a": {"name": "DK", "score": 1} },
    { "h": {"name": "DK", "score": 4}, "a": {"name": "NP", "score": 4} },
    { "h": {"name": "NP", "score": 1}, "a": {"name": "CBe", "score": 1} },
    { "h": {"name": "MK", "score": 1}, "a": {"name": "CBe", "score": 1} },
    { "h": {"name": "AB", "score": 0}, "a": {"name": "PG", "score": 1} },
    { "h": {"name": "JH", "score":1 }, "a": {"name": "CBe", "score": 4} },
    { "h": {"name": "JH", "score":2 }, "a": {"name": "MK", "score": 1} },
    { "h": {"name": "DK", "score":0 }, "a": {"name": "DG", "score": 4} },
    { "h": {"name": "DG", "score":2 }, "a": {"name": "CBo", "score": 0} },
    { "h": {"name": "DK", "score":3 }, "a": {"name": "AB", "score": 0} },
    { "h": {"name": "PG", "score":2 }, "a": {"name": "GT", "score": 0} },
    { "h": {"name": "DG", "score":3 }, "a": {"name": "DK", "score": 1} },
    { "h": {"name": "NP", "score":4 }, "a": {"name": "JH", "score": 0} },
    { "h": {"name": "MC", "score":5 }, "a": {"name": "CBo", "score": 0} },
]

current_ratings = {}
K = 20 # all matches are friendlies
INITIAL_RANKING = 1700

def rating(ro, k, w, we):
    return ro + k * (w - we)

def winexpect(dr):
    """
    winexpectancy should return a float between 0 and 1.0.
    
    dr is the rating difference
    """
    return 1 / (10 ** ( -dr / 400) + 1.0)

def resultscore(scorea, scoreb):
    if scorea > scoreb:
        return 1

    if scorea < scoreb:
        return 0

    return 0.5

def kmodifier(gd):
    #K is then adjusted for the goal difference in the game. It is increased by half if a game is won by two goals, by 3/4 if a game is won by three goals, and by 3/4 + (N-3)/8 if the game is won by four or more goals, where N is the goal difference.
    if gd >=4:
        return 1.75 + (gd-3)/8
    if gd >=3:
        return 1.75
    if gd >=2:
        return 1.5

    return 1

def ratingsformatch(match):
    hname = match["h"]["name"]
    aname = match["a"]["name"]
    hscore = match["h"]["score"]
    ascore = match["a"]["score"]

    chrating = current_ratings.get(hname, INITIAL_RANKING)
    carating = current_ratings.get(aname, INITIAL_RANKING)

    hres = resultscore(hscore, ascore)
    ares = resultscore(ascore, hscore)
    goaldiff = abs(hscore - ascore)
    hrating = rating(chrating, K * kmodifier(goaldiff), hres, winexpect(chrating - carating))
    arating = rating(carating, K * kmodifier(goaldiff), ares, winexpect(carating - chrating))

    return (hrating, arating)

for i in matches:
    (hrating, arating) = ratingsformatch(i)
    hname = i['h']['name']
    aname = i['a']['name']
    i["h"]["rating"] = int(hrating)
    i["a"]["rating"] = int(arating)

    current_ratings[hname] = hrating
    current_ratings[aname] = arating


sorted_ratings = sorted(current_ratings.iteritems(), key=operator.itemgetter(1))
sorted_ratings.reverse()
for (k, v) in sorted_ratings:
    print "%s\t%s" % (k, int(v))

print 

for i in matches:
    for (k,v) in i.iteritems():
        print "%s\t%s\t%s" % (v['name'],v['score'],v['rating'])
# The ratings are based on the following formulas:
# 
# Rn = Ro + K x (W - We)
# 
# Rn is the new rating, Ro is the old (pre-match) rating.
# 
# K is the weight constant for the tournament played:
# 
# 60 for World Cup finals;
# 50 for continental championship finals and major intercontinental tournaments;
# 40 for World Cup and continental qualifiers and major tournaments;
# 30 for all other tournaments;
# 20 for friendly matches.
# K is then adjusted for the goal difference in the game. It is increased by half if a game is won by two goals, by 3/4 if a game is won by three goals, and by 3/4 + (N-3)/8 if the game is won by four or more goals, where N is the goal difference.
# 
# W is the result of the game (1 for a win, 0.5 for a draw, and 0 for a loss).
# 
# We is the expected result (win expectancy), either from the chart or the following formula:
# 
# We = 1 / (10(-dr/400) + 1)
# 
# dr equals the difference in ratings plus 100 points for a team playing at home.
# 
# Sample Winning Expectancies
# Difference
# in Ratings	Higher
# Rated	Lower
# Rated
# 0	0.500	0.500
# 10	0.514	0.486
# 20	0.529	0.471
# 30	0.543	0.457
# 40	0.557	0.443
# 50	0.571	0.429
# 60	0.585	0.415
# 70	0.599	0.401
# 80	0.613	0.387
# 90	0.627	0.373
# 100	0.640	0.360
# 110	0.653	0.347
# 120	0.666	0.334
# 130	0.679	0.321
# 140	0.691	0.309
# 150	0.703	0.297
# 160	0.715	0.285
# 170	0.727	0.273
# 180	0.738	0.262
# 190	0.749	0.251
# 200	0.760	0.240
# 210	0.770	0.230
# 220	0.780	0.220
# 230	0.790	0.210
# 240	0.799	0.201
# 250	0.808	0.192
# 260	0.817	0.183
# 270	0.826	0.174
# 280	0.834	0.166
# 290	0.841	0.159
# 300	0.849	0.151
# 325	0.867	0.133
# 350	0.882	0.118
# 375	0.896	0.104
# 400	0.909	0.091
# 425	0.920	0.080
# 450	0.930	0.070
# 475	0.939	0.061
# 500	0.947	0.053
# 525	0.954	0.046
# 550	0.960	0.040
# 575	0.965	0.035
# 600	0.969	0.031
# 625	0.973	0.027
# 650	0.977	0.023
# 675	0.980	0.020
# 700	0.983	0.017
# 725	0.985	0.015
# 750	0.987	0.013
# 775	0.989	0.011
# 800	0.990	0.010