It’s amazing how small things can lead to upgrades, expensive or otherwise. I discovered media streaming to televisions over the summer, via the product ps3mediaserver, and that led to an interest in things like mplayer, ffmpeg, and avidemux. The demands of programs like that led to a motherboard upgrade, so now I have a 8 core AMD processor and 16 Gb of memory on my main desktop. Since 32 bit operating systems cannot address more than 4 GB at a time (though interestingly, the modern 32 bit pae kernels can handle 16 Gb of memory via paging tricks), I upgraded my main machine to Ubuntu 12.04, 64 bit.

Some notes: for those of you following my work technically, I’ll note that Maggie Xiong’s PDL::Stats does not like the version of PDL installed by Ubuntu 12.04 – that PDL is buggy – and CPAN does a poor job of trying to install PDL. It is best is to download the PDL module separately from CPAN and manually compile it. For one, you’re bound to find things you forgot to install and those extras will help give you a working product. Afterwards, you can compile PDL::Stats just fine.

John Turney, of the Pro Football Researcher’s Association, writes the blog about this article:

Shurmur ran an Eagle defense with the LA Rams and it was a double eagle defense, with 2 3-techs over the guards and a noseguard who was a linebacker by trade. The Eagle defense of Shurmur was very similar or identical to the 46.

Shumur’s book makes it clear, Eagle: The 5 LBer defense.

The only difference was in the personnel used. He used a linebacker in the place of the nose tackle and the defense ends. That allowed him to move that nose linebacker around if he wanted to and stem that guy to a standup linebacker and a variant of the Eagle called “Hawk”.

Shurmur did use a 3-4 as a base defense for Rams from 1983-90, but the Eagle was a sub defense they used for several reasons more often in 1988-90 than in 1985-87. In base situations with the Rams they were a 3-4 team. When the Eagle happened they’d pull the nose tackle Alvin Wright and LDE Doug Reed, and bring in extra linebackers to fill the spots in the Eagle.

So, the Eagle was an “eagle” and Shumur addresses this in his book. It was based on the Greasy Neale defense as well as the Buddy Ryan defense.

Thank you, John, for the correction. And for those of us who follow the Duece on Twitter, he tweeted an article from Strong Football about the Shurmer 5 LB defense, that pretty much lays out what John said above. That article is highly recommended. To borrow a diagram from that article, there is a position called nose backer, and he can be roughly where the Will backer is in a classic 4-3, or he can step into the line and function as a lightweight nose tackle.

Nose backer in the line, in the Eagle variant of the Shurmer 5 LB defense. Diagram originally from the Strong Football article referenced above.

Pretty cool, huh? At this point, I’d have to say that the Strong Football article is a must read for those of us interested in Eagle variants.

Stepping back to the beginning of preseason, there are at least two teams in the NFC East with lingering offensive line issues. I don’t have much insight presently into the state of the Giants or Redskins lines (feel free to speak up if you do), but you can see a fair amount of tweets and articles involving Philadelphia Eagle left tackle Demetress Bell. With the Cowboys, everyone who was considered a solution at guard (here, here, and here) and center, as of a couple months ago, is now injured. Guard has become something of a revolving door, and there is now talk of bringing in a veteran center, as Phil Costa is also injured.

In the jpeg below, there are some useful 2010 NFL stats.

2010 NFL metrics

Median is the median point spread from 2010. HS is Brian Burke’s Homemade Sagarin metric. I’m not as fond of either of these as I was when I was implementing them. I think that an optimized Pythagorean expectation is a more predictive metric than either of those two. Pythagoreans are in the PRED column, expressed as a winning percentage. Multiply the percentage by 16 to get predicted wins for 2011. SRS, MOV, and SOS are Pro Football Reference’s simple ranking system metrics. SOS is a factor in playoff wins, along with previous playoff experience. Home field advantage is calculated from the Homemade Sagarin metric. Take it for what it’s worth. Other topside metrics are calculated with the Perl CPAN module Sport::Analytics::SimpleRanking, which I authored. The HS was implemented using Maggie Xiong’s PDL::Stats.

This is a quickie post, as I’ve been working on a talk for the Atlanta Perl Mongers tonight. The topic is Chart::Clicker, the graphics software that Cory Watson has written. A lot of the graphs seen on this site were made with Chart::Clicker, and after learning a few new tricks, I now have this new plot of my winning versus draft picks chart.

Winning and draft picks per year are correlated.

Since Chart::Clicker doesn’t have an obvious labeling tool (that I can discover), I used Image::Magick’s annotate command (links here and here) to post process the plot.

I’ve been quiet a while, because I’ve been a little busy. A version of the simple ranking system, favored by Doug Drinen, is now coded as a CPAN module. CPAN, the Comprehensive Perl Archive Network, is a user contributed library, and thought to be Perl’s biggest strength.

The object that the SRS module creates can be used as the parent for other analysis, which is one reason for contributing it. A module that inherits function from the above also gets its game parsing functions for free. That’s one reason I went that route. Since I’m eventually wanting to think seriously about the “homemade Sagarin” technique  in a reproducible way, this is a place to start.

What I’m going to talk about now is an implementation of the Simple Ranking System in Perl. The Simple Ranking System is described on Pro Football Reference here. It’s important because it’s a simple – perhaps the simplest – model of the form

team strength = a(Point Spread) + b(Correction Factor)

where a and b are small positive real numbers. In SRS, a = 1 and b = 1/(total number of games played). The correction factor is the sum of the team strengths of all the team’s opponents.

The solution described by Doug Drinen on the Pro Football  Reference page isn’t the matrix solution, but an iterative one. You simply do the calculation over and over again until you get close enough.

(more…)

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