In my geekness, I maintain an unofficial ranking algorithm for New Zealands roller derby teams. Like any ranking system its a bit arbitrary and in my case all the more-so because there are no hard-and-fast rules as to which games should and shouldnt influence the rankings. As a rule of thumb, I include any game between domestic A or B teams and also some of the more stable invitational teams (Vagine Regime, Yeah Nah Bro and Frankenbeans). B teams, and even smaller leagues A teams) can be a bit problematic as sometimes they are half-filled with A-team players and pool players, and sometimes they are barely more than freshmeat cherry-popper teams, but I feel I have to include them because some of the lower ranked teams started out with very few bouts that werent against top leagues B squads. I dont include freshmeat bouts, where its clear thats what they are. I include short bouts, with their influence on rankings weighted by length - so a 30-minute bout has half the pull on ranking points that a full-length bout has. That too is an arbitrary decision. The two levers I have are how much each result influences the rankings and what influence playing at home makes to the predictions. I tweak the tuning of the algorithm in a number of different ways - trying to get, either for the current year or the whole data-set, either the best balance of home vs. away predictions or the lowest total error, or the greatest improvement in predictions. The interesting thing is that it now makes little difference which way I tune it, the results come out very similar. So where does everyone stand now? Well, up to and including last nights action and just looking at the A teams which have four or more results, the table looks like this (give or take a few points): Pts. Team 780 Pirate City 776 Richter City 732 Dead End 723 Auckland 712 Dunedin 710 Swamp City The above positions are stable regardless of how I tune the algorithm. ARDL have dropped out of 3rd spot into 4th after last night, but are still ranked ahead of DD, despite DDs win, due to their strong record in the past. It would be interesting to see SCRR, who lost a place to DD as a result of last night, play either of those teams. 694 Mount Militia 691 Hellmilton 680 K-Town 677 Whakatane 672 Sirens This section is the most volatile. The teams above are very close and small tweaks to the tuning of the algorithm moves them up and down relative to each other within the two groups. K-Town v. ARDL next week may settle the lower group (and maybe tangle K-Town up with MMDC and HRG, if they do well). 664 Bay City 655 Northland Nightmares 641 BoomTown 638 Taranaki 630 Otautahi 613 Whenua Fatales 581 River City 493 Hawkes Bay The placings at this end of the table are also stable, regardless of how I tweak the algorithm, only the distance between them changes by a few points. What do you think? Do these rankings and ratings look about right to you?
Posted on: Sat, 16 Aug 2014 23:03:57 +0000