*Preliminary NSFL ELO Ratings

[Beaver]

Thanks everybody, this is definitely a work in progress but it's a fun little project to play around with.

I suspect your k factor is a little on the high side. An 80 pt gain is a 160 pt swing.  That's way too much variance for one result IMO and a possible cause for rank inflation. This would also allow you to weight playoff games more. I'd probably go for 24 in the regular season and 32 in the playoffs. Just need to make sure your margin of victory adjustments don't allow it to extend beyond those limits probably.

Yeah that makes sense. I went with a k factor of 20 as a starting value since that's about what real life sports tend to be around so I think that 160 point swing was either just a massive outlier or my MOV adjustment is too lenient - bumping the k factor up to 24 turns that into a 192 point swing. The mean swing with these numbers is 42 points with a standard deviation of 32 so that 160 point swing was 3 and a half standard deviations above average. That standard deviation is a bit high for my liking but I'll revisit this after I make the adjustments, especially home field, as making the k value more precise is one of my priorities going forward.

Home advantage is also a must. In any implementation of the Elo rating system where home field is a factor, it is used (typically by adjusting rankings in the calculation) because it hurts the rating system to exclude it (and you get rank inflation). I'd suggest a rank advantage of about 150 pts as a test. I think it was JuOSu who did it before but can't remember what adjustment was made.

Yeah, this started out as an SHL project where I don't think there's a home advantage and I just completely blanked on including it. Unfortunately I'm a fairly casual NSFL member so I'm not super familiar with the sim we use. It looks like in an evenly matched game having home field would make win probability increase from 50% to 70% with a 150 point adjustment. Does that sound about right with the way the sim works? Time to do some testing.

Solid stuff though. You beat me to it with the margin of victory implementation (I was planning to use a variant of the system used for soccer) which was one of the things I noted as being missing from the last implementation we saw of Elo here.

I leaned heavily on this article (among others) in developing this and based my margin of victory adjustment on theirs (specifically footnote 2). This was fortunate for me because I had originally planned on going with something similar to the soccer system but I didn't really want a piecewise function out of my own laziness.

(Also why does everyone call these ELO ratings? It's Elo. Elo is a dude's name.)

That's a very good question. Habit, I suppose

Excellent stuff, though I disagree with some of your choices. You should go back and read my first post of my ELO ratings to see some of the different numbers I used. Otherwise great work.

As usual you beat me to it lmao. I'll definitely dig that up, appreciate the heads up.