Re: Offensive Power Rankings for 2008
 

ssCurious...what data or calculation changes explain the reduction of up to almost 3 points from the previous ranking for some teams listed? If the previous calculations were based on results through the 5th week regionals and there has been no additional results/data, what explains the changes observed for this list?

Re: Offensive Power Rankings for 2008
 

Since Sumadin and I went off of different data sets (him from TBA CSV's, me from usfirst.org) and used different algorithms, some perturbation is expected. There could've been a few missed matches in one of our data sets. This is my best guess for why there is a difference between our outputs.

Also, different methods of inverting the matrix could cause somewhat substantial differences in the floating-point input.

I haven't had the time to update my program to use TBA's CSV dump, so we won't be able to compare until probably tuesday when my classes end.

Re: Offensive Power Rankings for 2008
 

The Blue Alliance data includes elimination matches, which I would assume accounts for the majority of the difference. I think the result is probably better with only the qualifying matches.

The Blue Alliance data also gives scores of -1 for the missing peachtree matches (which are now in TBA database, so they would be included for the next data dump).

I've attached just the GTR qualifying matches (which I pulled from TBA's big dump) so that it is possible for sumadin to check his results against Bongle and Kyler's.

Re: Offensive Power Rankings for 2008
 

Our actual average score was 23.11 for our two regionals including penalties. You have us at 13.585. That's a huge difference.

I also see a couple of teams on your list that I know who's scores are way to high.

As I have said from the beginning the algorithm just won't work unless the penalties are somehow added in. They are just to important to this years game.

Re: Offensive Power Rankings for 2008
 

I don't think you're following what Bongle and others are doing. They're not calculating simple averages. They're using basic linear algebra to calculate the average expected value of pure points contributed to the alliance by a single team. This is used by setting up a system of equations which sum to the amount points scored at the regional. Since penalties are already removed from the final scores of all matches, this method takes them into account. The penalties are already "added in". This method is a far more accurate predictor of a team's contribution then just looking at a simple mean. Naturally you team's result is going to be lower than your average score, because this statistic is just looking at your team's contribution.

Re: Offensive Power Rankings for 2008
 

Here are my GTR numbers. If they look wrong, and someone java-literate feels like checking my algorithm, I'd love to send it to you.

Re: Offensive Power Rankings for 2008
 

Guy,

You might want to look into using Maple or Matlab. They're design for these types of computation, plus I'm sure you'll find plenty of other uses for them. I've found them to be indispensable tools.

Re: Offensive Power Rankings for 2008
 

They are exactly the same as Bongle's to 4 decimal places. Good job!

Re: Offensive Power Rankings for 2008
 

I was running the TBA data set. It seems that my numbers for GTR match Bongle's so the computation seems to be correct. Is it possible he isn't using elimination round scores? Because that might cause a drop.

Re: Offensive Power Rankings for 2008
 

Yeah, I didn't use elimination rounds because I feel they kind of distort the results. Playing matches with random robots against random opponents, I think you'll get a better feel for a team's contribution than when they are playing with a self-selected team against the creme de la creme at the regional. Although I guess if you want to take these numbers as scouting pointers rather than for entertainment value, a team's elimination performance is important.

For instance, take 1114 at GTR in the eliminators: they were playing with a team that they founded and they had won 3 regionals with. That team of robots will probably work together much better than a random team in qualifications, and so the scores will be different.

Another thing is that during eliminations, robots steadily get worn down: mechanisms break that can't get repaired in time, batteries slowly get discharged, motors overheat, and so you get things other than the team's competitiveness affecting the scoring level.

Plus, at a shallower regional like at waterloo, you'll end up with things like 1114/2056 against 3 teams who can't even hurdle, and the scores will be ludicrously high.

Said much better than I ever could.

Re: Offensive Power Rankings for 2008
 

I understand that, what I am saying is that their calculation of my teams expected contribution is no where near my teams actual contribution including subtracting the penalties.

Also I see several teams who's expected contribution is way to high from my experience of their performance this year.

If you guys want this tool to be useful you need to figure out why.

It's just my theory that it can't property calculate the impact of penalties, if you think this theory is wrong then you need to figure out what is causing the figure to be so different than the actual results.

Re: Offensive Power Rankings for 2008
 

Mathematically, this method is 100% sound. Whether you see any value in the mathematical model is for you to determine. I'd like to know your mathematical reasoning for why this method doesn't take penalties into account. If all you're relying on is selected cases of anecdotal evidence, your theory holds very little weight with me.

By no means am I suggesting that this model is perfect. From the numbers that Team 1114 has run, there are some definite anomalies. That being said, for the most part this model seems to agree with the specific match data we've collected at three events we attended.

Like with most statistics, the value is all in how you interpret them. If you don't think they're accurate, ignore them.

Re: Offensive Power Rankings for 2008
 

Just to emphasize the quality of OPR as a predictor of who will be playing on Saturday afternoon. Keep in mind, this was a 66 team regional, and predicting 24 robots out of the field is no small feat.

Here's the top 24 OPR from the GTR, and whether they were picked in the elims:

20/24 is a ridiculously decent hit rate. It should be higher since you couldn't expect this algorithm to predict that 703 would graciously withdraw.

Expect all good scouting teams to be using these stats in the very near future.

Re: Offensive Power Rankings for 2008
 

I am not a mathematician, I saw numbers that were wrong (not a little wrong, WILDLY wrong) and I posed a theory based on my feeling not on any math.

We are not competing in Atlanta so I have no need for this data, all I am saying some of what I see in spreadsheet is very wrong.

You can ignore it, I don't care.


Edit: I'll still buy you a doughnut in Atlanta.

Re: Offensive Power Rankings for 2008
 

All I understand is 1114 has an impressive score...
Which seems to fit their impressive robot.

Nice work... this will make a excellent tool to help newbies .