Offseason Training

What’s been happening lately at GRAFT?

Of course, I’ve set up the A-League site, and have been incrementally adding new things. Most recently putting together a SVG graph with the weekly fluctuations in the Elo ratings.

As well, I’ve made a some steps towards a decent prediction model. As you’d imagine “football” modelling is very mature and there is a great deal of literature on that, but you know, it doesn’t hurt to devise a system from first principles, even if you find out you’ve only reinvented the wheel at the end of it.

Elo is particularly good at giving you win/loss probabilities out of the box, but of course there’s the whole issue of draws to account for. On the whole draws seem to eventuate 25% of the time, which is a nice round figure.

This is one of the things I hope to deal with as I want to incorporate attacking/defensive ratings into the mix, in an attempt to create more plausible projections.

My theory is that a contest between two teams with attacking tendencies is less likely to result in a draw than between two more defensive teams. The reasoning should be fairly intuitive, if neither club gives a shit about stopping balls flying into nets, in such a shootout it’s less likely that the teams will finish on the same score.

As well, two evenly matched teams would be more likely to play out a draw than in a match where one team is of a much higher quality than the other, even when taking bus parking arrangements into consideration.

Anyway, that’ll take a bit of nutting out, although at the end, I want to be able to show a par score for each team prior to each game (much like I do with the AFL) although it’d look something like MVC 1.2 v SYD 2.1, with maybe the result probabilities alongside. The numbers would align to the poisson distribution of how many goals they might actually score. Once you get to that point, doing Monte Carlo predictions on that basis becomes pretty simple.

Among other moves for next year:

Revamp the site for the AFL/AFLW seasons in the new year. I mean, yes, it worked out for 2017, but I’m kind of bad about leaving things alone. Besides the whole “rating footy teams” part, I’m into this thing as much for developing new visualisations and designs. Basically I’m experimenting on all that in public. Some people have weird hobbies and this is mine.

Something else I will try and do is also provide CSV output of my tips and ratings into a set format so it’s easier for others to scrape and utilise rather than break everything whenever I mess around with the “look and feel”.

I consider the basic GRAFT system to be pretty much settled, for all its faults and limitations. That’s tied up with the basic philosophy that it takes into account only results and venues, however. It is what it is.

Which is not to say that I won’t have new things on the go, including other systems based off it or on completely different principles, but at the end of several years of development and refinement, the core is done. I do want to publish the basic algorithm (it really is absurdly simple) and some associated tools for others to examine and rip to shreds, but I am a horrible coder so there’s a bit of cleaning up to do before that happens.

Having said that, the main thrust of development is the projection system. I intend to overhaul the system that I use to work out my probabilities and eliminate some of the more egregious fudges. I’ll have more detail here during analysis and development, but the first aim is to move on from the “close enough is good enough” normal distribution that I have used up to this point.

As far as AFL projections go, I will probably stick to a continuous distribution. There’s a few that might fit the bill, but that’s yet to be figured out. Maybe gamma, maybe logistic. There’s a lot of number crunching to be done for that but I’m going for something that starts at zero and follows the historical curve, has some amount of covariance between the two teams, and of course it’ll need to correlate nicely with the GRAFT ratings.

Another objective with the AFL section is to flesh out history sections for the league in general and also under each club page. Not quite sure how to present all that, I probably won’t go all AFL Tables on you because, well, we already have AFL Tables, but having the ratings into a historical context would be interesting. Again, that’s a thing that will develop over time.

Aside from all the AFL stuff, there’s also the intention to¬† branch that other winter game – since I do want to have a more general view to the site. There’s a few things to work out how to tackle the NRL ratings, but I think some kind of hybrid approach will be needed there. Historical data is a little harder to find and organise so that’ll be the first thing to sort out. Of course this means I will might actually have to get enthusiastic about League again, which has been a struggle since it tried to go Super.

Of course in taking a more general approach across the sports, I have to sort out this shiny new site so people don’t get lost around here. Getting into the web dev side is pretty interesting; I’m using Bootstrap 4 as the basis for now since it’s reasonably easy to set things up so it doesn’t look too broken in small screens.

Aside from the framework, when it comes to generating the website pages, I’m committed to using all sorts of spaghetti code that I have trouble comprehending when I look it again after a break. Well, as I said, horrible coder. I probably do all sorts of things would make seasoned pros scream. “What’s unit testing, Precious?”

Fortunately it’s not my day gig, and I’m not looking for one.

Anyway, that’s what’s on the whiteboard for the next few months. In the next week or two I will have a poke at the 2018 AFL fixture and see how that stacks up and then announce my usual anodyne opinions about how nothing really matters anyway and thank buggery they haven’t inflicted us with 17/5 just yet. Bet you’re looking forward to that.

Changing of the Guard

So, that’s the winter sports all wrapped up for the year – at least in theory.

We saw Richmond triumphant in a game that saw them break down Adelaide’s vaunted attack while keeping up their own end. In particular, Dustin Martin had a fine game to sweep the treble of the Norm Smith, although like many I thought Bachar Houli might been a bit stiff missing out on that as he and Alex Rance did much to blunt the Crows’ path to goal. It was quite telling that when Martin turned up to the post conference he bore only the premiership medallion. Too much bling is gauche.

(As for the conspiracy theory that somehow Adelaide were stiffed by… something to do with umpiring or the higher gravity in Victoria or what, maybe if they hadn’t lost by eight goals, there might be grounds to establish an argument.)

Of course after Footy Christmas came Footy Boxing Day, with the Melbourne Storm just basically crushing the North Qld Cowboys, as seemed to be expected. A bit dull to watch but a nice send off for Cronk, Cam Smith and Slater. Also completing the Swan Street double after the Tigers’ incredible triumph sent that part of Melbourne into raptures – and without any overturned, burned out cars! Good work!

As far as GRAFT goes, I’ve decided to keep myself busy over summer by keeping track of the A-League which kicks off this weekend. The GRAFT system that I use for AFL doesn’t work so well for association football so I’ll be running off everyone’s favourite ranking algorithm as devised by Arpad Elo. I’m unlikely to bring too many enhancements beyond the off-the-shelf formula, although I do want to work out a method to track attacking/defensive alignment along the way. As such, the ratings for this season will be a work in progress as I tune things along the way. So it’ll be in alpha phase for this season.

I also have a bit of homework to do over summer as far as the AFL ratings go, mostly where it comes to projections and that. As I tweeted a while ago, the random algorithm I use for the Monte Carlo sims needs to reflect actual scoring distributions more closely so that’s going on the to-do list.