Monday, January 2, 2017

On Players Evaluation - Part IV (Teams Elo Projections)

On Players Evaluation - Part IV (Teams Elo Projections)

Part I
Part II
Part III

We left our reader at the point where we demonstrated how to produce Elo ratings for hockey teams over season (and over postseason too, if anyone wondered) and how to apply it to the up and coming next games of the rated teams.

However, in its main eparchy, chess, Elo is rarely used to produce single match outcome projections. It's much more popular when used to create a long-term projection, such as the whole tournament, which in chess lasts between five to thirteen rounds, usually.

Therefore, the question arises, shouldn't we try to use our newborn Elo ratings to long-term projections? And the answer is an unambiguous 'Yes!' We can and should create the projections for the team over longer spans such as a seven days ahead, thirty, or even through the end of the season!

How do we do it? Since we computed the Elo ratings for all teams, and we know the schedule ahead of all teams, we can run the Elo expectation on all matchups during the requested span and sum them. And since we assume that each team performs according the expectation, their Elo ratings do not change during the evaluation span.

Eteam = Σ(Ematch1, Ematch2, ... , Ematchn)

All good? No. There is one more finesse to add. The produced expectations will all be calculated in 2-0 span per game, assuming only 2 points are in play in each matchup. However, due to the loser's point it's not so. Therefore on average there are 2 + NOT/SO / Ntotal points are handed out during the season in every match (where NOT/SO is the number of games that get decided in OT or SO). So we need to compute the NOT/SO value, divide it by two (because there are two teams in each match) and multiply the expectation of each team by this factor. By doing so we receive the reliable Elo expectation, such as one in the table below, as of Jan 2nd, 2017. Spans of 7 days, 30 days and through the end of the season are displayed (games, expected points and total).

Elo ratings for season 2016
# Team Div Elo Pts Gin7 Pin7 Tin7 Gin30 Pin30 Tin30 GinS PinS TinS
1 Columbus Blue Jackets MET 2265.22 56 4 6 62 14 23 79 47 79 135
2 Pittsburgh Penguins MET 2186.57 55 1 2 57 11 16 71 44 65 120
3 Minnesota Wild CEN 2180.88 50 3 4 54 14 21 71 46 68 118
4 San Jose Sharks PAC 2137.87 47 3 4 51 14 20 67 45 62 109
5 Washington Capitals MET 2135.54 49 4 4 53 15 18 67 46 59 108
6 Montreal Canadiens ATL 2117.99 50 4 5 55 14 18 68 45 58 108
7 New York Rangers MET 2135.43 53 3 4 57 11 14 67 43 54 107
8 Chicago Blackhawks CEN 2103.27 51 3 4 55 12 15 66 42 52 103
9 Anaheim Ducks PAC 2105.41 46 3 4 50 13 18 64 43 55 101
10 Edmonton Oilers PAC 2092.89 45 4 4 49 14 16 61 44 53 98
11 Ottawa Senators ATL 2088.34 44 2 2 46 11 11 55 45 52 96
12 Toronto Maple Leafs ATL 2097.27 41 3 4 45 12 14 55 46 54 95
13 St. Louis Blues CEN 2066.58 43 2 2 45 12 12 55 44 51 94
14 Boston Bruins ATL 2079.41 44 4 5 49 15 17 61 43 49 93
15 Carolina Hurricanes MET 2093.06 39 4 5 44 13 13 52 46 53 92
16 Los Angeles Kings PAC 2066.68 40 4 4 44 14 16 56 45 52 92
17 Philadelphia Flyers MET 2079.35 45 3 3 48 12 13 58 43 46 91
18 Calgary Flames PAC 2076.79 42 4 5 47 14 16 58 43 49 91
19 Tampa Bay Lightning ATL 2068.90 42 4 4 46 13 14 56 44 48 90
20 New York Islanders MET 2070.87 36 2 3 39 12 14 50 46 51 87
21 Florida Panthers ATL 2059.66 40 4 5 45 13 14 54 44 46 86
22 Nashville Predators CEN 2055.15 38 4 4 42 14 14 52 46 48 86
23 Dallas Stars CEN 2052.77 39 3 3 42 13 13 52 44 46 85
24 Vancouver Canucks PAC 2049.05 37 4 5 42 12 15 52 44 46 83
25 Detroit Red Wings ATL 2033.62 37 3 3 40 13 12 49 45 43 80
26 Winnipeg Jets CEN 2017.50 37 4 4 41 14 14 51 43 40 77
27 Buffalo Sabres ATL 2009.45 34 3 3 37 13 12 46 46 41 75
28 New Jersey Devils MET 1994.66 35 5 4 39 14 12 47 45 37 72
29 Arizona Coyotes PAC 1921.41 27 3 2 29 12 8 35 45 30 57
30 Colorado Avalanche CEN 1910.42 25 3 2 27 12 7 32 46 29 54

The NOT/SO value right now is about 1.124 (i.e. about quarter of all games are decided past the regulation).

So you know what's good for the people?
But the people consists of men...

The team projection leaves us wanting more. After all, don't we want to be able to evaluate individual players and factor it somehow in the projection to reflect the injuries and other reasons that force top players out of the lineups? Stay tuned.

To be continued...

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