The Roller Derby community always enjoys a chance to add celebration to events, and Hallowe'en is a perennially popular time to indulge in a little theming of bouts.

As such, it's no surprise that Glasgow Roller Derby are continuing their tradition of a Hallowe'en bout with a fancy-dress competition as part of their Saturday double-header. The sporting component will also be exciting, with Tampere Roller Derby travelling across from Finland to face Glasgow's Maiden Grrders, and Lothian Derby Dolls taking on New Town Roller Girls in the opener.

The event starts at 12:30pm Saturday, at the ARC Sports Centre, Glasgow Caledonian University. The eventbrite tickets page is: https://www.eventbrite.co.uk/e/glasgow-roller-derby-maiden-grrders-vs-tampere-roller-derby-ldd-vs-ntrg-registration-19060101276 The Facebook events page is: https://www.facebook.com/events/1093676273994184/

Meanwhile, up in Dundee, Dundee Roller Girls' Home Season continues, with the Jammin' Dodgers playing the Press Gangsters. Excitingly, the event will be a double-header, with Scotland's National Men's Derby team, Power of Scotland, engaging in a selection bout between the 30 training team members for the current squad. Not only will this bout feature the best of Scottish Men's Derby, but it will also feed into the final 20 Power of Scotland members to make up the National Squad going into the next Men's Roller Derby World Cup in Calgary 2016.

The event starts at 12:30pm Saturday, at the Dundee International Sports Centre, Mains Loan. Tickets available from Brown Paper Tickets: http://www.brownpapertickets.com/event/2155922 The Facebook events page is: https://www.facebook.com/events/739368379522055/

With the excitement of most of the travel season behind them, the home season for Auld Reekie Roller Girls and Dundee Roller Girls is just about to begin. In fact, both leagues are holding their first home teams games this coming weekend.

We know that Auld Reekie's three teams - The Skatefast Club, Leithal Weapons and Cherry Bombers - have all been actively preparing for the coming season, with various scheduled scrims against all comers, so we're sure that this will be a tightly contested season. The first bout, starting at 2pm at regular venue Meadowbank Stadium, sees last season's victors, The Skatefast Club, take on the Leithal Weapons (who, as previous winners, will be wanting to regain that title). There will be a licensed bar, and half-time entertainment!

Meanwhile, Dundee's Jutes of Hazzard, Jammin’ Dodgers and Press Gangers have also been hard at work, to judge from their team twitter accounts. Their first bout is actually a double feature, opening with some Junior Derby from Fierce Valley Roller Cubs, before last season's winners, the Press Gangers, take on the Jutes of Hazzard! You can catch them at Dundee's regular venue, the Dundee International Sports Centre, at 1230.

Auld Reekie Roller Girls

Tickets page: http://www.brownpapertickets.com/event/2252536  (individual bout pricing, plus a discounted rate for a season ticket)

Facebook Events page: https://www.facebook.com/events/1697429183819893/

Dundee Roller Girls

Tickets page: http://www.brownpapertickets.com/event/2155922

Facebook Events page: https://www.facebook.com/events/743992315727456/

For those of you planning to follow Glasgow Roller Derby's debut at WFTDA Division 1 Playoffs, you might like to have the timetable in the UK Time Zone.

Luckily, UKRDA's Julie McCrann has already done this for you, with a Google spreadsheet available here:

https://docs.google.com/spreadsheets/d/1dl2QolV9wZYLO7KR-blepizkPTiqSt9PPvpOw9XNCq0/edit#gid=870394344 

Glasgow's first bout will be at 5pm tonight (18 September) against Charlottesville Derby Dames.

If they win, then their next bout will be at 11pm against Denver Roller Girls, otherwise they will play the loser of game 3 (probably Tampa Bay) at 5pm tomorrow (19th September).

Remember that, if you're in Glasgow, GRD has arranged a series of viewing events which you can keep up with here.

Otherwise, you can always watch live at WFTDA.tv.

As we mentioned in our last analytics article, the work we've been doing on Roller Derby analytics is now sufficiently advanced that our predictions about last week's Division 1 Playoffs were just as good as those of Flat Track Stats. We think that this is probably good enough to start making a few public predictions - and where better than in this weekend's coming Division 1 Playoffs.

In particular, this playoffs is yet another history-making event, with Glasgow Roller Derby attending as the first ever Scottish league to reach Division 1, and only the second UK league after London Rollergirls! (Last week was similarly historic for Sweden, with Crime City Rollers and Stockholm Roller Derby both attending for the first time.)

The WFTDA prediction for this playoffs is: 1. London Rollergirls (#4) 2. Denver Roller Derby (#5) 3. Jacksonville RollerGirls (#9) 4. Atlanta Rollergirls (#13) 5. Tampa Roller Derby (#18) 6. Detroit Derby Girls (#21) 7. Glasgow Roller Derby (#26) 8. Steel City Roller Derby (#29) 9. Pikes Peak Derby Dames (#36) 10. Charlottesville Derby Dames (#38) corresponding to the seeding for the tournament itself (numbers in brackets are the WFTDA rank).

Both we and Flat Track Stats disagree with this prediction somewhat, and in generally the same areas. We tend to consider Steel City somewhat underranked, and Pikes Peak somewhat overranked, but differ as to precisely how much. Using score ratios, our prediction for the final standing is: 1. London Rollergirls 2. Denver Roller Derby 3. Jacksonville Roller Girls 4. Atlanta Rollergirls 5. Tampa Roller Derby 6. Detroit Derby Girls 7. Steel City Roller Derby 8. Glasgow Roller Derby 9. Charlottesville Derby Dames 10. Pikes Peak Derby Dames

and using score difference simply swaps the position of Glasgow and Charlottesville. In fact, by both metrics, the Glasgow / Charlottesville bout is predicted to be the closest bout of the entire tournament, with potentially less than 20 points between the two! This bout is on at 5pm Friday, UK time. You can watch it live on WFTDA.tv, or attend the Glasgow Roller Derby viewing party!

Flat Track Stats predicts (with its idea of the WFTDA rank in brackets): 1. London (#2) 2. Denver (#7) 3. Jacksonville (#8) 5. Atlanta (#16) 5. Tampa (#18) 6. Detroit (#20) 7. Steel City (#23) 8. Pikes Peak (#41) 9. Charlottesville (#43) 10. Glasgow (#50)

although it also agrees that the Glasgow/Charlottesville bout will be extremely close (giving Glasgow a 37% chance of winning)!

In previous analytics posts, we've discussed the potential for least-squares ("Massey") methods as a mechanism for predicting Roller Derby team scores, and used a primitive version to analyse the performance of the Women's and Men's World Cups. At the time, we mentioned that a significant issue for least-squares fits is that, by default, they treat all data equally - there's no sense in which an older result is "superseded" by newer results automatically.

Subsequently, we also posted some results on determining the connectivity of Roller Derby, showing that nowadays there is one dominant group of Derby teams, internationally, who have all played at least one other member of the group in the last year. This work also allows us to measure how rapidly this group grows over time (starting from a given date, how long does it take for the majority of teams to have played sufficient games that all of them are connected in this way). Given the time-dependance issues of Least-squares methods, we use this data to sample only enough bouts to capture the largest group (this turns out to require between 7 and 9 months worth of bouts at any point in time).

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Optimisation

There are two potential improvements to our least-squares algorithm over the "vanilla" default version. Firstly, we can attempt to compensate for home advantage by adjusting the scores for the home team by a small amount relative to reality (removing their theoretical advantage). Secondly, we can attempt to provide some "time awareness" by weighting old results relative to newer ones, so the influence of any given bout reduces over time. The difficulty is determining the precise values for these two corrections.

Using the Flat Track Stats datasets, we ran searches across the potential values for the two corrections (using 7 months of bout data to produce predictions, and then testing them against the subsequent month, for each value). There's quite a flat region of good performance for both, but we determined that a home advantage correction of around 0.1 to 0.15, and an exponentially-decaying weight with time-base on the order of 3 months gave the best results.

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Results

In order to test our model, what better subject than the WFTDA Division 1 Playoffs, which are increasingly international with each year. We generated predictions for both score-ratios and score-differences for each of the bouts in the WFTDA Division 1 Playoffs 2 (held 11-13 Sept 2015), using both unoptimised and weighted-optimised versions of our Least-Squares model.

When calculating the expected score ratios, we can compare directly against the performance of Flat Track Stats (which publishes expected score ratios for all bouts). The FTS predictions were taken from the site on the 11th and 12th of September, so FTS predictions for the second day of the Playoffs included data from the first day.

(Our model was run on the dataset ending on the 8th September for all predictions, using bouts from 1 Jan 2015 through to that date (approximately 9 months).)

We can plot the resulting predictions, along with the actual score ratios (using a logarithmic scale) here:

Plot of FTS, Least-squares (optimised) and Real log score ratios for WFTDA Division 1 Playoffs 2.

In general, our model does at least as well as Flat Track Stats does at predicting score ratios - we both fail at the Crime City v Rose bout by some margin, but also have many close matches to our predictions in other situations. This is perhaps easier to see by plotting the difference between the real score ratio and the predictions, for FTS and our model:

Plot of absolute prediction errors for FTS, Least-squares (optimised) for log score ratios, WFTDA Division 1 Playoffs 2.

We can measure our overall performance by computing the Mean and RMS error - the Mean error gives a measure of our systematic bias (if as many of our guesses are high as low then they cancel out), while the RMS error gives a value for generally how bad our guesses were in general.

For Division 1 Playoffs 2, both our Mean and RMS errors are smaller than those of FTS (-0.135 v -0.330 for Mean error - showing that we both slightly underestimate on average; 0.476 v 0.607 for RMS error). In both cases, the dominant contributor to the error is the Crime City bout, although we still outperform FTS even if that particular bout is removed. (In fact, even without optimisation, standard Least-Squares outperforms FTS on these metrics.)

Surprisingly, if we try to predict on the basis of Score difference, rather than Score Ratios, we do considerably better in precisely the extreme cases that cause ratio methods problems. (Here, we can't compare against FTS, as they do not publish score difference predictions.)

Plot of Least-squared (optimised) prediction and Real score difference results, WFTDA Division 1 Playoffs 2

Interestingly, although the Score difference prediction does better than we expected, it does fail to predict the winner as often as the Score ratio prediction: Score-diff calls 4 bouts wrongly, while ratios call 3 (and FTS 5), although there is considerable overlap across the bouts each find problematic.

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Conclusion

We have established an optimised Least-Squares predictor for Roller Derby bouts, and tested it on WFTDA Division 1 Playoffs 2 bouts. We appear to be at least as successful as the more technologically sophisticated Flat Track Stats algorithm at predicting score ratios (potentially because ELO ranking metrics find sparse competitor graphs more difficult to handle), although neither algorithm has what we would regard as a superlative degree of predictive ability.

In our next article, we will publish some predictions for WFTDA Division 1 Playoffs 3, featuring London Rollergirls and Glasgow Roller Derby.

(In future, we hope to explore some other sport ranking algorithms, notably the pi-rating used as the basis of Constantinou's pi-football prediction system. Like soccer, Roller Derby has highly volatile bout performance, so we hope that pi-rating will be able to improve on both of the systems in this article.)

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Acknowledgements

This analysis was performed using the September 8 dump of the Flat Track Stats bouts and teams databases. This data is released under a Creative Commons 4.0 Non-Commercial license. In the spirit of this license, which permits all uses which are not-for-profit, this article and the data in it are also released under a Creative Commons 4.0 Non-Commercial Share-Alike license - this means that you may use this article in any way which is not-for-profit, as long as you license your derived work in the same way.

As Capital City's next game and the final  game of 2015's Scottish Men's Roller Derby Nationals (SMRDN) against Mean City  creeps ever closer we would like you all to find out a little more about two new faces that will be on track that day, so we asked them a few questions. Mad Science and Darth Evader will be making their Scottish debut at the game for Capital City, although this is not Mad Science's first game. He traveled down south with Capital City a couple of Months ago when they went to play Manchester's Chaos Engine, but this will be his first game in Scotland.

Darth Evader #54

Mad Science #36

Mad Science #36  (MS) Darth Evader #54 (DE)

How did you find out about Derby and CCRD? DE:   I discovered derby through my girlfriend who was making a short documentary on roller derby. I found out about CCRD by looking online for men’s roller derby teams in Edinburgh and there they were! MS:  Through my flatmate who is also a member of the team. I joined because I wanted to learn to skate but quickly fell in love with derby.

Having not skated previously how did you find working towards and passing your mins? DE:   I found them to be a mix of easy and hard tasks. Some of the mins just clicked and others took a while to get the hang of but they were always the most rewarding mins to tick off. MS:  Mins gave me a well-structured set of basic skating skills to work on and allowed me to measure my progress. During training my teammates would share their insights and offer valuable feedback but in skating everyone has their own technique and part of the process was figuring out my way of doing things. A lot of it is muscle memory so repetition is the key. Passing mins gave me the confidence that I can skate well enough to play without hurting myself or anyone else.

Mad Science and Darth Evader - Picture by V.L. Tickle

What would you say has been your biggest achievement so far in derby? DE:   Learning to do crossovers has to have been the most rewarding thing I’ve ever learned to do. I’d seen loads of skaters do it and couldn’t wait to learn myself and once I did I felt pretty damn good about myself! MS: Being part of the team. Growing up as a gay kid and a big nerd, not only did I dislike sports but had particularly hard time playing in a team. In roller derby I learn to anticipate my team’s course of action and to adapt my play accordingly. This requires good communication and trust, which develop gradually over time.

Did you have any pre first bout nerves before your game down in Manchester? MS: Of course, I only look like a cold-blooded Vulcan. I was never worried about falling or making a fool of myself but I was really anxious about letting my team down.

Mad Science - Picture by V.L. Tickle

Did you get any good advice that helped you on track or prepare for the bout? MS: What put me at ease was an advice from Tequila Jammer: “Remember to be safe and to have fun.” I was so in my head that I forgot that roller derby is about having great fun.

Is there any advice you could give others who still have their first bout to come? MS: Roller derby requires well-trained reflexes and good technique and that can make novice players uncomfortable, especially when playing next to more seasoned and perfected players. But roller derby is a very fast-paced sport, which means that everyone is bound to make mistakes. Don’t worry about your mistakes, just focus on doing your best. Remember that your team is there for you.

Mad Science - Picture by V.L. Tickle

Have you had any pre first bout nerves so far? DE: I get nerves just thinking about a bout let alone actually taking part. I imagine that’ll pass a couple of jams in though.

Have you had any good advice so far to help you prepare for the bout? DE: Some of the best advice given to me was to just take it easy in the first few jams of a bout until the adrenaline kicks in, and this advice really has helped.

Darth Evader - Picture by V.L. Tickle

Are there any skaters (Male or Female) who inspire you? DE:   I’ve taken a lot of inspiration from all of the skaters at CCRD they all have different styles and I try to put different parts of their experience into my own performance. I also take a lot from the way Rose City’s Loren Mutch plays--or I try to at least! MS:  Space Invader (Boston Derby Dames) who is an agile and powerful jammer and an effective blocker. She also sports a very fashionable piece of eyewear, definitely my kind of a rebel. I also look up to a number of members of my own team not only for their outstanding technical skills but also for creating an atmosphere where you have fun and want to excel. I’ve been training for over half a year now and there’s never been a training that didn’t get me pumped with energy.

Skaters generally set goals for themselves, now that you have played in your first bout what goal’s are you now looking to achieve/work towards? DE:   Someday, I’d like to make POS and to do that I probably need to work on every part of my game. So in the short term that’s my main goal. MS:  I have the advantage of being stable and quite powerful but the downside is relatively low agility and difficulty with fine speed control, which I need to work on. Also to be a more effective team member, I need to work on my awareness of what is going on in the game and where I’m needed.

Darth Evader - Picture by V.L. Tickle

You can see Mad Science and Darth Evader play in the final game of this years Scottish Men's Roller Derby Nationals at Meddowbank on Saturday the 19th of September, for more information visit the event page.

Coming soon to Edinburgh, Lothian Derby Dolls will play Aberdeen's second ever derby team, as Granite City Roller Girls launch their B-squad, the Fight Hawks. We caught up with Fight Hawks Bench Manager, Pert Hits, to find out a bit more. (Season Tickets for the bout on the 12th, and LDD's two subsequent games, can be obtained from Brown Paper Tickets.)

Granite City are only the fourth Scottish league to form a B-team (after ARRG, GRD and DRG). How does it feel to be able to launch a second travel team? 

It feels natural.  With the roster sort of set for the Northern Fights, it had left a fair few of our skaters with no games to play, which was a real real shame given the calibre of skaters we are seeing coming through our fresh meat course (a number of whom completed the 3 month course and passed all mins first time!).  As the number increased over the course of the year, it just felt like the right time for it to happen.

Can you tell us a little about the makeup of the team, and the selection process? Are these all new skaters to GCRG fans?

We had a look at the sheer number of mins passed skaters we had that were not dedicated to the British Championships and who were game ready.  Various things were looked at, perhaps the more important factors were attendance to training and scrim practice.  The team selection will be quite fluid as time goes on with different players perhaps being selected for each game.  Of the 14 skaters submitted for our first game, only 4 of them will be familiar faces to GCRG fans.  The rest may have been spotted in various "cherry poppers" across Scotland to those with a keen eye.

GCRG B are named 'The Fight Hawks'. Obviously, this continues the 'Fight' theme with GCRG A 'Northern Fights', but which Night Hawks (the painting, perhaps?) were you inspired by, and what do you hope it says about you?

We are actually named after a local term for seagulls, which we have in Aberdeen in abundance.  A quick youtube search and you can see why we went with this name; they're brash, brave and persistent.  And we will steal your chips when you're not looking.  But we do pay for Doritos, so please feel free to invite us for game.

Your first bout is away against Lothian Derby Dolls, down in Edinburgh. How are you preparing for the bout? What result are you hoping for?

With British Champs winding down for the Northern Fights, we are in a good position to have our training sessions tailored directly towards the Hawks' needs. As bench and line-up, myself and Krusty have been watching like... hawks... as the girls train and giving feedback to our training committee, who have been very good at taking it into account and getting the right drills we need. We have also been doing "Hawks vs the rest" at scrim practices just to ensure the team meld and we get a good hive mind. We are heading down to Edinbrugh looking to score more points. Perhaps the more important win, however, is knowing we gave 100% and played well as a team. Even defeats on the score board feel like wins if you know you did your best and worked well as a team.

What're the Hawks' plans for the future? With GCRG A committed to British Champs, will you guys be taking on more eclectic teams?

I am not entirely certain what the future holds for us. I would certainly be expecting a good jaunt around Scotland in 2016, playing various teams, and with the right amount of fundraising taking our team a little further afield would a dream!

This year we saw the launch of the Scottish Men's Roller Derby Nationals (SMRDN), which saw Bairn City Rollers, Mean City and Capital City all fight for the bragging rights of being the top Scottish Men's team. With two games played and two wins to BCR's Skelpies they have taken the title of champions for this year. There is however still one more game left to play which is sure to be an exciting clash for more than one reason, which is Capital City vs Mean City.

These two teams have yet to met on track in a public game, with this their first encounter deciding who will take second place in this years SMRDN and the looser picking up 3rd and last place for 2015. With so much to play for, both teams will be fighting for every point from the first whistle to the last. And if this wasn't enough to tempt you along, Capital City have turned the event into a double header.

To get everyone ready for the main event, they are putting on a coed game first at which we will get to see some of the the Granite City Brawlermen in action for the first time as they join forces with some of the girls from Granite City Roller Girls as well as other guys and girls from the likes of Capital City, Mean City and Bairn City to form both of the coed teams.

This double header will take place at Meddowbank on Saturday the 19th of September, for more information visit the event page.

AULD Reekie Roller Girls’ InARRGuration bout for the league’s newest competitive skaters and guests was a victory for all. A close-run game saw Green Eggs and SLAM! Leading with 123 points to Team Nazgul’s 99 at half-time. But the second half saw the Nazguls race back to score 223 to 184 for a stonking win. Team Nazgul Captain Powerhouse said the pre-game secret weapon was team brownies. She said: “We prepared by having a meeting over drinks in the Auld Hoose to discuss rules, default tactics, any worries or issues. “Then we had many more chats on our Facebook group - I think this helped our guest skaters a lot, and helped them feel part of the team. “On the day, the wonderful vice-captain, Radge of Honour made amazing brownies, and I made (equally as amazing, but less tasty) posters. “These had some simple focuses for the bench (keep positive, calm and zen) and on track (have fun, communicate and stay together). “There was also a pink elephant, amongst other beautiful artwork, which really got the point across.” Green Eggs and Slam Captain Hex said fizz helped the green team bond. She said: “We had loads of chat on Facebook and then we all met up at vice captain Dead Metal's house for a meeting where we talked rules and strategy and watched derby on the telly. “We may also have drunk some fizzy drinks...” Hoose and Hex both admitted in the thrill of the game they barely checked the score. Hex said: “I wasn’t actually really looking at the score. “I noticed we were in the lead at half time and yeah! It felt good! “I felt like we were doing really well and the score reflected that.” Hoose said: “Once both teams settled into the game, I felt we were well matched and I was having so much fun, I barely looked at the scoreboard! “Our bench coach, the inimitable Collie, used our team time outs really wisely, when we were able to take a breath, refocus and get back out on track raring to go. “I think the gap in points spurred us on, and the green team really forced us to bring our top game - they were incredibly strong, aggressive with some fantastic offence.” Hex said the turning point was half-time, when four Green players fouled out. She said: “Oh dear, I think the turning point was our penalties. “Everyone was giving their all and sadly it was maybe a bit too much! “Players started to foul out and the bench was getting shorter as people were tiring. “Team Black were also totally amazing!!!” The second half was where Hoose felt the team came into their own because of their focus. She said: “There were a few jams in a row where more than one green player was in the bin. “The black team managed to keep their cool, keep low, slow and strong (SO PROUD), and take total advantage of this. “Our fantastic line up manager, Gerry, noticed this and put on some really smart line ups, with fast jammers. “Once we pulled away, it was going to be difficult to catch us, and added to that, there were a few foul outs on the green side - that's always going to be exhausting! “The boost of focus carried over into the rest of the game, raised the quality of derby, and the rest is history.” After the game, both teams headed to the pub. Hoose said there were many sweaty hugs and lots of beer to celebrate everyone’s hard work. She said: “It was such a great experience, and I think everyone learned a huge amount. “I'm incredibly proud of both teams, and so grateful to ARRG, and all the officials and volunteers on the day! “It didn't matter who won or lost. As clichéd as it sounds, we all won - every single person now has the experience of a well matched, well played game under their belt. That's invaluable. “We all developed skills, and tried things we never thought we could do - we are now better skaters, and have a bunch of new friends to talk derby with! Hex agreed derby love was the order of the day.

She said: “There were lots of hugs and lots of derby love! It was great how close you get in a couple of hours! “Then not so healthy food and drink with greens, blacks, refs, nsos -- all the best people you could hope to hang out with! “There were incredible vibes - how much all the skaters put their heart and souls into it and what an amazing team we created having never met half of the skaters before, how much hard work the organisers had put into it, all the refs, nsos, announcers, audience - everyone involved! I just felt spoiled rotten to be a part of it all! best day EVA!”

What a day - what a lovely day!

Mean City Roller Derby’s coed team will make their competitive debut on Saturday, August 22, at the ARC sports centre in Glasgow.

The Glasgow league – which is open to people of all genders and none – are rostering a team of men and women for the first time in a public game.

It comes less than a year after the league voted to become coed – with Mean City's membership on the rise.

The event on August 22 has a distinctly dystopian feel – entitled Mad Macs.

Captain Gordon Hendry said: “According to Fury Road, the future belongs to the Mad - but we reckon it belongs to the Mean.

“To celebrate Mean City becoming the first coed league in the West of Scotland, we have got together with some lovely skaters across the country to present a coed bout with class written through it like a stick of rock.

“In the purple and silver corner, wearing battered leather and a grizzled grin are the men and women of Mean City Roller Derby.

“And in the blood-splattered white corner are Furiosa's Furies - some of Scotland's most talented - and toughest - skaters.

“It’s going to be marvellous, mad and – above all – it’s going to be Mean. We've been training hard for this and genuinely can't wait. Get your tickets now."

Since becoming a coed league, Mean City Roller Derby’s membership has grown and grown.

In fact, demand is so strong that the league has organised another fresh skater intake – Tuesday, September 1 at the ARC – 7.15-9pm.

For more information, visit www.facebook.com/MeanCityRollerDerby