Sunday, November 4, 2018

Introducing roboCap: An automated horse race handicapper

For last year's Breeders Cup, I unveiled my first attempt at betting market rankings for thoroughbred horses. I publish similar rankings for a variety of sports, including the NBA, the WNBA, the NFL, College Football and Basketball, Major League Baseball, and, most recently, the NHL.

After quite a long hiatus, I have started republishing these rankings here, and they will update weekly going forward (after the Sunday races are run). In addition, I have created a new tool, roboCap, that uses these rankings to create projected closing odds for any chosen field of horses. The rest of this post gets into the technical details of how this all works, but if you just want to play around with it, here's a quick guide:
  • Enter the track take at the top. This is how much the track takes off the top from the win pool. You can find take percentages for most tracks here. This is needed to accurately project the odds. The higher the take percentage the lower the projected odds (lower odds = higher probabilities). The Churchill Downs track take is 17.5%.
  • Enter the horse names in the first column (autocomplete should help you out). To be in the tool, the horse must have run at least one race in the last 180 days.
  • Click "Handicap!" and the tool will return projected closing odds, along with true win probability and GLA, or Generic Length Advantage. Generic Length Advantage is the source of the projections and represents expected margin of victory (in lengths) against an average thoroughbred in a one mile race.
  • If a horse isn't in the database, or you disagree with the ranking, check the "Override" box and input your own GLA and click "Handicap!" to recalculate the odds.