APBRmetrics

YaoPau · Joined: 28 Jan 2009 Posts: 35

I created a Statistical Offensive APM which uses TS% along with OREB%, AST%, TOV%, USG% which I regressed against Aaron's '07-'08 numbers. I posted the results at http://www.3hoopsfans.com/2009/03/expected-opm/ . My excel is available for download there at both the middle and bottom of the page.

Edit: If you don't feel like combing through my lengthy post for the download link, here's the spreadsheet: http://spreadsheets.google.com/ccc?key=peZQH7tnbE07s0HlWipWiUg

YaoPau · Joined: 28 Jan 2009 Posts: 35

Carlos · Joined: 21 Jan 2005 Posts: 64 Location: Montevideo, Uruguay

Interesting work. It would be good to check how does it correlate teamwise with teams's Off. Eff. as compared with other linear weights ratings (for example, Offensive PER).

mtamada · Joined: 28 Jan 2005 Posts: 377

Mountain · Joined: 13 Mar 2007 Posts: 1527

Is Ariza a defensive specialist? Maybe not clearly a specialist by the numbers against al opponents but the Lakers have him playing one on tv.

Defense specialist + passing + 3 point game. Bowen, Battier Bell have that 3rd ingredient. Ariza takes the shot too and is at least average. 11% assist% basically ties him for the lead for your set of current names.

A steal for what they paid for him.

Walton and Odom are different mixes on these 3 variables but I have no doubt the Lakers are looking to get some impact from each on these 3 and getting some of all 3 was a factor in them being there over others who might be less 3 dimensional even if they were better on one.

Artest would seem to be one the leading candidates for being like a Michael Cooper type or beyond. I hadn't really given him or Houston's staff enough credit for climbing back to 41% FG on 3 pointers. Turkoglu and Ginobili are high on the criteria too. They are too good for inclusion on your defensive specialist list but I mention them anyways.

Offensive APM - EOPM essentially is non-boxscore offensive impact and Offensive APM error. How much is each, hard to say but it is certainly not all error. Each case is a different mix but on average are they similar sized?

Maybe you get some better results for wingspan in combo with draft combine agility score and possibly vertical leap even though quickness of jumping would be a better indicator?

**Ilardi** · Joined: 15 May 2008 Posts: 265 Location: Lawrence, KS

YaoPau · Joined: 28 Jan 2009 Posts: 35

YaoPau · Joined: 28 Jan 2009 Posts: 35

fundamentallysound · Joined: 18 Jul 2008 Posts: 25 Location: VA

Hi all, just wanted to see if I couldn't resurrect this thread, because I was playing around with YaoPau's EOPM, and had a thought about how it might be improved, and how we might use what we know about the Four Factors to use relatively simple rate statistics to create a better EOPM and EDPM.

First, I'd like to say that I really like YaoPau's work here and don't mean for this to come off as disparaging at all. However, there's some interesting stuff that comes as a conclusion from his findings on the importance of AST% in estimating offensive adjusted plus minus. It seemed to be suggested (and I seem to remember some of his comments on Blog-a-Bull hinting at this as well) that being a good passer is a heavy component of being a positive offensive player by adjusted plus minus. I would like to challenge that notion for a couple of reasons.

First, AST% is more of a measure of a player's role within an offense than his intrinsic passing ability. For instance, Tyrus Thomas had AST percentages of 6.6% and 11.0% in his first two years in the league, under Scott Skiles's offense. Then, in the isolation heavy Del Negro offense of last year, he managed a paltry 5.5% AST%. Does that mean that Tyrus was suddenly a worse passer? Hardly. The same phenomenon happened to John Salmons coming over from the Kings to the Bulls. Salmons went from having an AST% of 17.3% to dropping all the way to 8.8% in the same year all because the offense that he was working within called for more isos from him and less passing opportunities that would result in scores. It stands to reason, though, that a player that's being asked to shoulder a heavy load in the offense (by way of a high AST%) would probably be pretty offensively talented and very likely to have a positive OAPM. But, this effect is already captured by Usage or preferably, DeanO's Possessions Used.

Second, assists are a pretty subjective stat and they aren't correlated at all to winning via the Four Factors. Great offenses can be primarily isolation heavy or they can be focused on ball movement and finding the open man. There are all sorts of ways to achieve success, so I find it rather dubious that at the individual level that AST% is really as useful as the correlation might be indicating to us. Correlation, of course, does not always equal causation and I think this is a case of that. I believe the causation, as I mentioned above, is just that the same players that are offensively talented enough to post high OAPMs are also very often called upon to be distributors on their team.

For those two reasons, I would eliminate AST% from his EOPM a re-run the regression. Similarly, I would use FTM/FGA and eFG% instead of TS%, because it's relatively simple to use those two aspects of the Four Factors rather than the slightly simpler, but less accurate version of them, TS%. Finally, and perhaps most radically, I would use raw +/- as part of the regression to figure out the correlation between raw +/- and adjusted +/-, when OReb%, eFG%, FTM/FGA, TOV% and USG% are accounted for. Unfortunately, I am not educated enough in the ways of excel, R, or otherwise to run such a regression, but I figure that the raw data is all available, and it would be relatively easy for those of you who are so inclined to run this regression on the 6-year noise reduced 2008-09 apm figures that have been provided elsewhere in this forum.

On the other side of the ball, I would like to see a regression done with DReb%, BLK%, STL%, Personal Fouls per 100 possessions (maybe), and raw defensive +/- (from 82games). Those figures seem to be the best proxies for Four Factors on the defensive side on the individual level that we have, so I think coming up with an EDPM or Statistical +/- (whatever you want to call it) based on them would be useful.

I think running these two regressions would likely give us very good statistical estimates of offensive and defensive adjusted plus minus, which would be useful in reducing the noise of single year APM.

Anyone that is capable and willing to do this work, please do. I'd really like to see the results.

Mike G · Posted: Fri Oct 16, 2009 6:42 am Post subject: Re: Resurrecting this thread

YaoPau · Joined: 28 Jan 2009 Posts: 35

FS, thanks for the interest in EOPM and bringing up some legitimate concerns. I'm glad to know somebody's still looking at that old site Smile

You questioned whether AST% should be component of statistical APM because it can vary wildly from year to year based on a player's role in an offense. But APM only rates how effective a player was in his role, that season. Tyrus Thomas's AST% dropping doesn't mean he's less skilled at passing now than in 2008, it means he didn't pass as much, and thus wasn't contributing as much to the Bulls via his passing. It's not his fault, that's just what happened in VDN's system, and all we can do is estimate Tyrus's effect within that system.

Passing, as the data suggests, has a HUGE correlation with offensive APM, and I don't think it makes sense to toss it out considering the importance of passing. It's backed up, I think, by this article from 82games which shows a strong correlation between touches per second and offensive rating (scroll down a quarter way).

Are assists subjective? Somewhat. But no stat is perfect. Rebounds are dependent on who's on the floor with you, USG% as well. The point is to get an estimation of what the player is doing, and it looks like assists do a decent job of accounting for passing.

As for your suggestion that: "the same players that are offensively talented enough to post high OAPMs are also very often called upon to be distributors on their team." In many cases, that's not true. Look at the offensive APMs for Kevin Martin, Kevin Durant, Amare Stoudemire compared to Brad Miller, Kevin Garnett, Pau Gasol. High USG% doesn't necessarily correlate with high AST% (our own Ben Gordon is a great example), but AST% reigns in its correlation with APM.

As for statisticals in general, I tried a defensive statistical using the categories you listed and got around a .4 correlation. Doesn't work. I'm mining some other data right now to try to improve on it.

But I have improved EOPM by a metric shitload. I ran 4 year APMs, accounted for garbage time, and left each year unweighed so I could use them directly in a regression. Then I regressed them against TS%, OREB%, DREB%, AST%, STL%, BLK%, TOV%, USG% and got a .699 correlation. Will post soon.

fundamentallysound · Joined: 18 Jul 2008 Posts: 25 Location: VA

YaoPau · Joined: 28 Jan 2009 Posts: 35

My fault, I didn't see the raw +/- part. I had run a regression a couple months back with DREB%, BLK%, STL%, PF/40 and position played and got .4.

I agree raw +/- could help, but I don't love the idea of using an input that's so dependent on teammates. Hinrich was +6.4 raw defensively last year. Stick him behind Iguodala instead of Gordon and he's probably negative.

fundamentallysound · Joined: 18 Jul 2008 Posts: 25 Location: VA