[Axon and Zillgitt] Mark Cuban, Dallas Mavericks involved in petition regarding racial discrimination at arena

LieutenantKumar · 2018-03-30T15:22:51+00:00

I just checked your history. Your link got removed because you forgot to place the author's name in the title.

LieutenantKumar · 2018-03-30T01:52:56+00:00

Consider this. If one thing only models 60% of another thing, shouldn't you use that other thing?

DRPM is basically BPM x RAPM

There's also PIPM like you linked, and PT-PM.

And now there's all types of luck adjusted RAPMs.

At the end of the day, I'm not a big fan of using any of them as anything more than a baseline.

LieutenantKumar · 2018-03-30T01:18:29+00:00

But when the makers of the stat openly say there are better defensive stats out there and that "Basically, the regression can't account for the wide spread in defensive value" There becomes little point in using it for anything meaningful.

You can go ahead and use it if you like tho

LieutenantKumar · 2018-03-30T00:04:25+00:00

If I say that a spoon is not a particularly good shovel, it doesn't mean the spoon can't be used to dig. But it doesn't mean I should use it to dig or give it consideration when thinking about what tools I can use.

If something is not good, then why use it? You'd have to make a pretty big excuse to use it. To believe you can use DBPM as a measure of defense would be to believe you can learn all there is to learn about a player's defense just from the box score.

LieutenantKumar · 2018-03-29T23:50:36+00:00

You can look at his comments in the ABPR forum, DBPM is dismissed. But also his own comment on reddit where he explicitly says:

BPM is not particularly good at measuring defense, as others have noted. It's working based purely on team success and the box score. It struggles for DBPM particularly in two areas: it sometimes will overvalue REALLY BAD offensive players, since why are they on the floor other than their defense? And it also struggles with crazy good offensive players; their total BPM numbers are quite big and BPM will sometimes push too much of that credit to the defensive side of the accounting. That happens with very high interaction term players that have great numbers with usage, assists, and rebounding at the same time.

LieutenantKumar · 2018-03-29T23:44:02+00:00

Do you not see the issues if a stat can only explain 62% of the variance of another stat that it is DESIGNED to model?

And again, I don't know why you're so bent on dismissing the words of the guy who made the stat.

LieutenantKumar · 2018-03-29T23:31:20+00:00

Also from Jacob himself about the assist prior:

"It’s more indicative of the type of player someone is. Generally, high assist players are players who aren’t great at defense. So including it in the boxscore version is more accurate than not. But then the on-off data helps to adjust back for players who break that mold."

LieutenantKumar · 2018-03-29T23:08:06+00:00

Yes, BPM is removed from what it's actually trying to predict, and is operating with a pretty large raw information deficiency compared to stats like RPM, because it doesn't have play-by-play. That doesn't mean it should have close to zero weight.

You haven't explained to me why it should have weight. I've given you the statments of the guy who created the stat and given you an explanation on how it's calculated. Neither of those suggest it should have DBPM should be taken with any seriousness.

And that article from Nylon Calculus is for another stat to estimate RAPM instead of BPM. The reason assists have value isn't some notion of IQ, it's because made baskets contribute to defense. And assists contribute to made baskets. That's why the prior is small.

LieutenantKumar · 2018-03-29T22:10:24+00:00

I went in pretty thorough detail why it's bad question in first place.

LieutenantKumar · 2018-03-29T21:56:55+00:00

I don't care to learn why assists correlate to defense as much as I care that it does correlate to defense.

But they don't. They correlate to overall BPM. You subtract OBPM and what is left gives you DBPM.

The shots I showed you above showed you a breadown of where that leftover value was coming from. The implication there is that you can almost dismiss any value associated with assists.

And the quote from the creator above is him being very kind to DBPM on BBref's official page. In APBR forums, he's basically dismissed it. Especially since BPM doesn't take in play-by-play data and only takes in the box score.

And think about this. BPM is designed to model RAPM which is designed to model point differential. It's twice removed from the primary object.

Edit: Here is a direct comment from him on reddit lol

BPM is not particularly good at measuring defense, as others have noted. It's working based purely on team success and the box score. It struggles for DBPM particularly in two areas: it sometimes will overvalue REALLY BAD offensive players, since why are they on the floor other than their defense? And it also struggles with crazy good offensive players; their total BPM numbers are quite big and BPM will sometimes push too much of that credit to the defensive side of the accounting. That happens with very high interaction term players that have great numbers with usage, assists, and rebounding at the same time.

LieutenantKumar · 2018-03-29T21:38:16+00:00

That operates under the assumption that being top 20 in DBPM is meaningful and accurate in the first place, which it isn't.

Here is a break down of some "top 20" players in DBPM. You can see that most of them get the majority of their value from the "Rebounding and Versatility" column (assists), and not the actual "Defense" column. Davis is the only one of those six that gets his value actually from "defense".

Link

Even still, the whole notion of DBPM as explained by the creator is as follows:

Defensive BPM is simply overall BPM minus offensive BPM. The offensive BPM regression was tuned to minimize weighted squared error on both offensive and defensive RAPM simultaneously.

They don't actually try to calculate or it, it's leftover assigned value.

This is also what he had to say about it:

There are limitations on all box score stats – if the box score doesn't measure a particular contribution, a box-score-based metric can only approximate that contribution. This is not a great hindrance on the offensive side, as nearly everything of importance on offense is captured by the box score (only missing things like screen-setting), but on defense the box score is quite limited. Blocks, steals, and rebounds, along with minutes and what little information offensive numbers yield about defensive performance are all that is available. Such critical components of defense as positioning, communication, and the other factors that make Kevin Garnett and Tim Duncan elite on defense can't be captured, unfortunately.

What does this mean? Box Plus/Minus is good at measuring offense and solid overall, but the defensive numbers in particular should not be considered definitive. Look at the defensive values as a guide, but don't hesitate to discount them when a player is well known as a good or bad defender.

LieutenantKumar · 2018-03-29T21:15:50+00:00

That's not how statistical support works.

LieutenantKumar · 2018-03-29T21:09:00+00:00

That is hilariously incorrect with no statistical basis of support.

LieutenantKumar · 2018-03-29T20:13:43+00:00

Not at all. DBPM has virtually 0 bearing on defense.

LieutenantKumar · 2018-03-29T19:19:41+00:00

There is also a lot of information on confirmation bias, and seeing things we wanna see.

Also stuff like this: http://www.theinvisiblegorilla.com/gorilla_experiment.html

LieutenantKumar · 2018-03-29T14:37:43+00:00

For future reference please follow the tweet formatting rules. Thanks!

LieutenantKumar · 2018-03-28T16:20:33+00:00

He has Rondo as his top five - who neither stats nor the eyes test favors. Who cares if it's Gary Payton. He clearly doesn't watch these guys.

LieutenantKumar · 2018-03-28T16:18:35+00:00

No he hasn't. I watch him every night.

LieutenantKumar · 2018-03-28T15:18:45+00:00

bbref does positions based on height. He's taller than all of our other guards

aannnd that's a crappy technicality

LieutenantKumar · 2018-03-28T13:19:49+00:00

Rondo over Jrue? I'm crying man. This a damn shame

LieutenantKumar · 2018-03-28T05:17:28+00:00

I mean Jrue and Rondo playing like this is a more recent development. And one of the major reasons they weren't better than 27-21 was defense. Pels were forced to start an undersized perimeter that featured 1 plus defender. Pels were putting up a top 5 offense, but a bottom 10 defense.

There's a reason when lineups like

D.Cousins, A.Davis, J.Holiday, D.Miller, E.Moore were +38.0

I.Clark, D.Cousins, A.Davis, J.Holiday, E.Moore +27.4

D.Cousins, D.Cunningham, A.Davis, J.Holiday, E.Moore + 6.7

Solomon Hill's injury hurt the Pelicans a ton.

In the first year of Boogie, the Pelicans proved they could be an elite defense with him. This year they proved they could be an elite offense. What part of that doesn't fit?

It's just lazy superficial analysis on your part and not watching the games.

LieutenantKumar · 2018-03-28T04:44:11+00:00

Gentry said he was calling for one.

LieutenantKumar · 2018-03-28T04:37:26+00:00

1) Lebron has a negative net rating for the season. Negative. Does anyone believe the Cavs are better without him?

2) If a team's issues could be pointed out by net ratings alone, there would be no need for people to cover any team.

3) Rondo - since Boogie went down team has been a +0.4 with him. Since ASG they have been +5.3. Also when Rondo plays seven-plus minutes in 4th quarters, Pelicans are 16-2 this season and have won 12 consecutive games. In those 4th quarters, he has 53 assists and seven turnovers.

No one has been a bigger critic of Rondo this season than I have, but even I can see that he's stepped it up and has been helpful in other ways. There is a lot of factors that go into how a team is performing on the court. The way you're going about it to conclude AD and Boogie aren't a great fit is a lazy way to do so.

You won't find stats that say one of our "good" players makes us so much worse

Blazers have a -0.5 net rating with CJ McCollum. Only +5.1 when Both CJ and Lillard are together, -4.3 when Lillard is off. Literally the same argument you make for AD and Boogie.

LieutenantKumar · 2018-03-28T04:18:54+00:00

I don't know why you're so insistent on trying to explain me the issues of a team I cover. Those on off stats barely even cover the surface of the team dynamics.

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