Is it a Good Time to be a Mariners Fan? Ranking Baseball Teams Using Linear Algebra By Melissa Joy and Lauren Asher
How are sports teams usually ranked? Winning Percentage system: The team with the highest percentage of wins is ranked first. Problems: If all the teams do not play all the other teams then your winning percentage depends on how good the teams you play are. Possibility of ties Solution: Linear Algebra…
MLB 2006 Regular Season (through April 17 th ) Los Angeles Angels (A) Seattle Mariners (B) Oakland Athletics (C) Texas Rangers (D) A vs. B: W 5-4 L 8-10 L 4-6 A vs. D: W 5-2 W 5-4 L 3-11 B vs. C: W 6-2 L 0-5 L 0-3 C vs. D: L 3-6 W 5-4 L 3-5 Sum of Points Scored in the 3 games A vs. B: A vs. D: B vs. C: 6-10 C vs. D: 11-15
How to find the ranking vector According to Charles Redmond, the vector yielding the ranking has this formula:
1/3 1/3 0 1/3 1/3 1/3 1/ /3 1/3 1/3 1/3 0 1/3 1/3 Sum of rows represents the number of games played Sum of the rows =1 Making an Adjacency Matrix
Sum of Points Scored in the 3 games A vs. B: A vs. D: B vs. C: 6-10 C vs. D: A: = -7 B: = -1 C: = 0 D: = 8 Finding an S vector
1/3 1/3 0 1/3 1/3 1/3 1/ /3 1/3 1/3 1/3 0 1/3 1/3 Eigenvalues: = 1 = -1/3 = 1/3 Eigenvectors: Normalized Eigenvectors: ½½½½½½½½ ½ -½ ½ -½ 1/√ /√2 0 1/√ /√2 Solving for Eigenvectors
A Linear Decomposition of S /2 -1/2 1/2 -1/2 1/√2 0 -1/ √2 0 1/√2 0 -1/ √ / √2 -9/ √2 -5/2 5/2 -5/2 5/2 -7/2 0 7/2 0 -9/2 0 9/2
Plugging S into the Limit The limit can be expanded into the decomposed form of S The eigenvalues are substituted in for M/3 The limit becomes:
The Final Ranking -7/2 0 7/2 0 -9/2 0 9/2 -5/2 5/2 -5/2 5/
And the winner is… Texas Rangers (D) 2.Oakland Athletics (C) 3.Seattle Mariners (B) 4. Los Angeles Angels (A) This ranking is based on points. It is a better early season predictor because: Measures skill rather than simply wins and losses Eliminates ties