Thursday, October 25, 2012

2012-10-24: NFL Power Rankings Week 8


After running the R script for the week 8 rankings, the first thing that struck my mind was the disparity in the size of the nodes between the AFC on the left side of our graph and the NFC on the right side.

Two weeks ago we wrote that the NFC West has been dominant so far this year. The NFC West has the best combined record and their aggregate point differential puts others to shame.  However it is not just the West division but the entire NFC conference has dominated and out-performed the AFC conference at every turn. CBS Sports rates the NFC as head and shoulders above the AFC this year.

Our ranking system is based on Google's PageRank algorithm. It is explained in some detail in past posts. A directed graph is created to represent the current years season. Each team is represented by a node in the graph. For every game played a directed edge is created from the loser pointing to the winner and it is weighted by the Margin of Victory. 

In the Pagerank model each link from a webpage i to webpage j causes webpage i to give some of its own Pagerank to webpage j.  This is often characterized as webpage i voting for webpage j. In our system the losing team essentially votes for the winning team with a number of votes equal to the margin of victory. Last week the Giants beat the Redskins 27 to 23, in the graph a directed edge from the Redskins to the Giants with a weight of 4 was created.

The season graph so far can be visualized in the following graph.


The Pagerank algorithm is run and all of the votes from losing teams are calculated. The nodes in the graph are given a final ranking and that is represented by the size of the node in the graph. This algorithm does a much better job of taking the strength of schedule into account than many of the other ranking systems that are essentially based on win loss ratios. Barring any injuries or or other problems it is a good guess that Houston will representing the AFC once the playoffs are complete. The real question is which team from the NFC will rise to surface to take them on in the Superbowl.

The numerical rankings are as follows:

RankTeam
1San Francisco
2Green Bay
3NY Giants
4Dallas
5Chicago
6Seattle
7Minnesota
8St Louis
9Washington
10Houston
11Arizona
12Atlanta
13Baltimore
14Philadelphia
15Cincinnati
16Denver
17New England
18NY Jets
19Indianapolis
20Pittsburgh
21Buffalo
22Miami
23Detroit
24San Diego
25New Orleans
26Cleveland
27Tennessee
28Carolina
29Tampa Bay
30Oakland
31Jacksonville
32Kansas City

-- Greg Szalkowski

No comments:

Post a Comment