APBRmetrics

feyki wrote:For the 1975 , Wes Unseld has a higher DBPM than Elvin Hayes . But Elvin Hayes had both more steals and blocks than Unseld. Only advantage of Unseld is Defensive Rebounds.

How is this possible , statistically ?

I don't have any information about calculation of Defensive BPM . I wish
anyone help me here .

Statman wrote:

feyki wrote:For the 1975 , Wes Unseld has a higher DBPM than Elvin Hayes . But Elvin Hayes had both more steals and blocks than Unseld. Only advantage of Unseld is Defensive Rebounds.

How is this possible , statistically ?

I don't have any information about calculation of Defensive BPM . I wish
anyone help me here .

I assume it's assist rate.

I'm not joking.

Someone will probably post with the formula.

Crow wrote:DBPM doesn't give accurate individualized play by play shot defense, so it is missing around 1/3 of total defensive value. I'll pass by it and see what it says but I don't consider it good enough to really trust / use beyond a basic lean in most cases.

538 Carmelo projections took a big step back when it went from 50/50 RPM / BPM to all BPM, imo.

BPM may be pretty good on average and for many middle of the distribution players but it is highly suspect on the overall tails and specific stat tails, imo.

AcrossTheCourt wrote:It's because of the influence of AST%*TRB%, which is pretty big overall in the formula, even on defense.

http://www.basketball-reference.com/about/bpm.html

I also think high USG% players get penalized in DBPM just for having high USG%.

Dr Positivity wrote:It's a good observation. As mentioned it looks like TRB% and Ast% combination

I think BPM from that long ago is somewhat sketchy anyways. I mean it's better than nothing, but it's built on +/- evaluating what's valuable in the modern era, whereas 1975 is a different game with no 3s, transition play having a whole different level of meaning, no turnovers tracked and steals/blocks before 1974, etc. The league has changed a ton in even just 15 years with the rise of pick and roll dominated 3pt shooting teams vs posting up and the rise of analytics/player tracking and game preparation etc. resources, let alone 40.

Crow wrote:Shot defense covered here viewtopic.php?f=2&t=9223

feyki wrote:For the 1975 , Wes Unseld has a higher DBPM than Elvin Hayes . But Elvin Hayes had both more steals and blocks than Unseld. Only advantage of Unseld is Defensive Rebounds.<br abp="1310"><br abp="1311"> How is this possible , statistically ?<br abp="1312"><br abp="1313"> I don't have any information about calculation of Defensive BPM . I wish<br abp="1314"> anyone help me here .

╔════╦═════════════╦═════╦════╦════╦══════╦═════╦══════╦═══════╦════╦═════╦═════╦═════╦══════╦═══════╦═════╦═════╦═══════╦═════╦══════╦══════╦═════╦═════╦═════╦═════╦═════╦══════╦══╦══════╦══════╗
║ Rk ║   Player    ║ Age ║ G  ║ GS ║  MP  ║ FG  ║ FGA  ║  FG%  ║ 3P ║ 3PA ║ 3P% ║ 2P  ║ 2PA  ║  2P%  ║ FT  ║ FTA ║  FT%  ║ ORB ║ DRB  ║ TRB  ║ AST ║ STL ║ BLK ║ TOV ║ PF  ║ PTS  ║  ║ ORtg ║ DRtg ║
╠════╬═════════════╬═════╬════╬════╬══════╬═════╬══════╬═══════╬════╬═════╬═════╬═════╬══════╬═══════╬═════╬═════╬═══════╬═════╬══════╬══════╬═════╬═════╬═════╬═════╬═════╬══════╬══╬══════╬══════╣
║  1 ║ Elvin Hayes ║  29 ║ 82 ║    ║ 3465 ║ 9.6 ║ 21.8 ║ 0.443 ║    ║     ║     ║ 9.6 ║ 21.8 ║ 0.443 ║ 5.3 ║ 7   ║ 0.766 ║ 2.9 ║ 10.2 ║ 13.1 ║ 2.7 ║ 2.1 ║ 2.4 ║     ║ 3.1 ║ 24.6 ║  ║      ║   88 ║
║  2 ║ Wes Unseld  ║  28 ║ 73 ║    ║ 2904 ║ 4.3 ║ 8.5  ║ 0.502 ║    ║     ║     ║ 4.3 ║ 8.5  ║ 0.502 ║ 2   ║ 2.9 ║ 0.685 ║ 5   ║ 11.8 ║ 16.8 ║ 4.6 ║ 1.8 ║ 1.1 ║     ║ 2.8 ║ 10.5 ║  ║      ║   88 ║
╚════╩═════════════╩═════╩════╩════╩══════╩═════╩══════╩═══════╩════╩═════╩═════╩═════╩══════╩═══════╩═════╩═════╩═══════╩═════╩══════╩══════╩═════╩═════╩═════╩═════╩═════╩══════╩══╩══════╩══════╝

╔════╦═════════════╦═════╦════╦══════╦═════╦═══════╦══════╦═══════╦══════╦══════╦══════╦══════╦══════╦══════╦══════╦══════╦══╦═════╦═════╦══════╦═══════╦══╦══════╦══════╦═════╦══════╗
║ Rk ║   Player    ║ Age ║ G  ║  MP  ║ PER ║  TS%  ║ 3PAr ║  FTr  ║ ORB% ║ DRB% ║ TRB% ║ AST% ║ STL% ║ BLK% ║ TOV% ║ USG% ║  ║ OWS ║ DWS ║  WS  ║ WS/48 ║  ║ OBPM ║ DBPM ║ BPM ║ VORP ║
╠════╬═════════════╬═════╬════╬══════╬═════╬═══════╬══════╬═══════╬══════╬══════╬══════╬══════╬══════╬══════╬══════╬══════╬══╬═════╬═════╬══════╬═══════╬══╬══════╬══════╬═════╬══════╣
║  1 ║ Elvin Hayes ║  29 ║ 82 ║ 3465 ║  19 ║ 0.496 ║      ║ 0.32  ║ 6.4  ║ 22.7 ║ 14.5 ║ 8.7  ║ 2.1  ║ 2.9  ║      ║      ║  ║ 4.3 ║ 8.2 ║ 12.5 ║ 0.173 ║  ║ 0.3  ║ 3    ║ 3.2 ║ 4.6  ║
║  2 ║ Wes Unseld  ║  28 ║ 73 ║ 2904 ║  15 ║ 0.538 ║      ║ 0.338 ║ 11   ║ 26.2 ║ 18.6 ║ 12.7 ║ 1.8  ║ 1.3  ║      ║      ║  ║ 4   ║ 6.6 ║ 10.6 ║ 0.175 ║  ║ 0.3  ║ 5.2  ║ 5.5 ║ 5.5  ║
╚════╩═════════════╩═════╩════╩══════╩═════╩═══════╩══════╩═══════╩══════╩══════╩══════╩══════╩══════╩══════╩══════╩══════╩══╩═════╩═════╩══════╩═══════╩══╩══════╩══════╩═════╩══════╝

Crow wrote:If want to put shot defense into an equation, I'd look at counterpart shot defense and team shot defense while actually on court, convert the data from NBA.com to points allowed above or below average per x minutes or 100 possessions, taking account of both effectiveness and frequency of opponent possession usage, then blend the two at a ratio of 50-70% counterpart and 50-30% team shot defense. Put that in winshares / 48 (or BPM or DRE or a new metric by you) instead of the undifferentiated value by individual and time on court that is there.

Or use DRPM in a 50/50 blend with the suggested above or alone instead of any other stat / metric for defense.

Or hope for 4 factor RPM values again or calculate them yourself and use the shot defense factor found there instead of the shot defense estimate suggested above.

( Use a box score / rpm blend for offense, perhaps at 70/30 or 50/50.)

Or use PT-PM or Dredge.

The worse option is settling for the no shot defense of PER or the very poor estimates in ws/48 or BPM. DRE's globbed on shot defense to other defensive stats might be slightly better than ws/48 or BPM at least to the level of bigs vs. perimeters, but it is probably not as good as estimating by my method or as part of DRPM or by separate RPM factor.

DSMok1 wrote:

feyki wrote:For the 1975 , Wes Unseld has a higher DBPM than Elvin Hayes . But Elvin Hayes had both more steals and blocks than Unseld. Only advantage of Unseld is Defensive Rebounds.<br abp="1310"><br abp="1311"> How is this possible , statistically ?<br abp="1312"><br abp="1313"> I don't have any information about calculation of Defensive BPM . I wish<br abp="1314"> anyone help me here .

Nice find, feyki!

First of all, a quick background on how DBPM is calculated. http://www.basketball-reference.com/about/bpm.html

The variables and interaction terms in BPM were developed to best match long term RAPM.

OBPM and DBPM are based on the same secondary regression, which was tuned to split the total BPM into offensive and defensive components. So all of the variables in primary BPM were used in this secondary regression, with the target of the regression being to minimize squared error for OBPM and DBPM simultaneously. So every stat is used in DBPM, not just steals and blocks. Basically the BPM regression goes:
1. What is our estimate for this player's RAPM?
2. What is our best estimate for how to split that estimate into offense and defense?

Note: this approach had equivalent or lower error than directly running a regression on DRAPM.

So, now that we know that all of the stats are involved, what's causing this situation?

Here are their stats per 100 possessions:

Code: Select all

╔════╦═════════════╦═════╦════╦════╦══════╦═════╦══════╦═══════╦════╦═════╦═════╦═════╦══════╦═══════╦═════╦═════╦═══════╦═════╦══════╦══════╦═════╦═════╦═════╦═════╦═════╦══════╦══╦══════╦══════╗
║ Rk ║   Player    ║ Age ║ G  ║ GS ║  MP  ║ FG  ║ FGA  ║  FG%  ║ 3P ║ 3PA ║ 3P% ║ 2P  ║ 2PA  ║  2P%  ║ FT  ║ FTA ║  FT%  ║ ORB ║ DRB  ║ TRB  ║ AST ║ STL ║ BLK ║ TOV ║ PF  ║ PTS  ║  ║ ORtg ║ DRtg ║
╠════╬═════════════╬═════╬════╬════╬══════╬═════╬══════╬═══════╬════╬═════╬═════╬═════╬══════╬═══════╬═════╬═════╬═══════╬═════╬══════╬══════╬═════╬═════╬═════╬═════╬═════╬══════╬══╬══════╬══════╣
║  1 ║ Elvin Hayes ║  29 ║ 82 ║    ║ 3465 ║ 9.6 ║ 21.8 ║ 0.443 ║    ║     ║     ║ 9.6 ║ 21.8 ║ 0.443 ║ 5.3 ║ 7   ║ 0.766 ║ 2.9 ║ 10.2 ║ 13.1 ║ 2.7 ║ 2.1 ║ 2.4 ║     ║ 3.1 ║ 24.6 ║  ║      ║   88 ║
║  2 ║ Wes Unseld  ║  28 ║ 73 ║    ║ 2904 ║ 4.3 ║ 8.5  ║ 0.502 ║    ║     ║     ║ 4.3 ║ 8.5  ║ 0.502 ║ 2   ║ 2.9 ║ 0.685 ║ 5   ║ 11.8 ║ 16.8 ║ 4.6 ║ 1.8 ║ 1.1 ║     ║ 2.8 ║ 10.5 ║  ║      ║   88 ║
╚════╩═════════════╩═════╩════╩════╩══════╩═════╩══════╩═══════╩════╩═════╩═════╩═════╩══════╩═══════╩═════╩═════╩═══════╩═════╩══════╩══════╩═════╩═════╩═════╩═════╩═════╩══════╩══╩══════╩══════╝

And here are their "advanced" stats:

Code: Select all

╔════╦═════════════╦═════╦════╦══════╦═════╦═══════╦══════╦═══════╦══════╦══════╦══════╦══════╦══════╦══════╦══════╦══════╦══╦═════╦═════╦══════╦═══════╦══╦══════╦══════╦═════╦══════╗
║ Rk ║   Player    ║ Age ║ G  ║  MP  ║ PER ║  TS%  ║ 3PAr ║  FTr  ║ ORB% ║ DRB% ║ TRB% ║ AST% ║ STL% ║ BLK% ║ TOV% ║ USG% ║  ║ OWS ║ DWS ║  WS  ║ WS/48 ║  ║ OBPM ║ DBPM ║ BPM ║ VORP ║
╠════╬═════════════╬═════╬════╬══════╬═════╬═══════╬══════╬═══════╬══════╬══════╬══════╬══════╬══════╬══════╬══════╬══════╬══╬═════╬═════╬══════╬═══════╬══╬══════╬══════╬═════╬══════╣
║  1 ║ Elvin Hayes ║  29 ║ 82 ║ 3465 ║  19 ║ 0.496 ║      ║ 0.32  ║ 6.4  ║ 22.7 ║ 14.5 ║ 8.7  ║ 2.1  ║ 2.9  ║      ║      ║  ║ 4.3 ║ 8.2 ║ 12.5 ║ 0.173 ║  ║ 0.3  ║ 3    ║ 3.2 ║ 4.6  ║
║  2 ║ Wes Unseld  ║  28 ║ 73 ║ 2904 ║  15 ║ 0.538 ║      ║ 0.338 ║ 11   ║ 26.2 ║ 18.6 ║ 12.7 ║ 1.8  ║ 1.3  ║      ║      ║  ║ 4   ║ 6.6 ║ 10.6 ║ 0.175 ║  ║ 0.3  ║ 5.2  ║ 5.5 ║ 5.5  ║
╚════╩═════════════╩═════╩════╩══════╩═════╩═══════╩══════╩═══════╩══════╩══════╩══════╩══════╩══════╩══════╩══════╩══════╩══╩═════╩═════╩══════╩═══════╩══╩══════╩══════╩═════╩══════╝

Let's see--first of all, the BPM regression sees Wes Unseld as likely to have the better RAPM. Why? Hard to say without diving deep into the numbers, but players with versatility (able to assist, rebound, and score) typically do well. Also, volume scoring is only valuable in BPM if the player is a passing threat as well. There's a usage x ast interaction term.

So, after calculating the overall BPM, the secondary regression splits the BPM value into two halves. The big components in this are offensive volume, steals, and blocks. So Elvin Hayes had more steals and blocks, but RAPM shows that volume scorers on the offense are typically poor defenders on the other end, their defensive stats notwithstanding. And versatile players like Unseld typically are good defenders, their defensive stats notwithstanding.

So most of Wes Unseld's impact is assigned to the defensive end.

This is a very interesting case, and I appreciate you bringing it up! Did my explanation make sense?

Crow wrote:If want to put shot defense into an equation, I'd look at counterpart shot defense and team shot defense while actually on court, convert the data from NBA.com to points allowed above or below average per x minutes or 100 possessions, taking account of both effectiveness and frequency of opponent possession usage, then blend the two at a ratio of 50-70% counterpart and 50-30% team shot defense. Put that in winshares / 48 (or BPM or DRE or a new metric by you) instead of the undifferentiated value by individual and time on court that is there.

Or use DRPM in a 50/50 blend with the suggested above or alone instead of any other stat / metric for defense.

Or hope for 4 factor RPM values again or calculate them yourself and use the shot defense factor found there instead of the shot defense estimate suggested above.

( Use a box score / rpm blend for offense, perhaps at 70/30 or 50/50.)

Or use PT-PM or Dredge.

The worse option is settling for the no shot defense of PER or the very poor estimates in ws/48 or BPM. DRE's globbed on shot defense to other defensive stats might be slightly better than ws/48 or BPM at least to the level of bigs vs. perimeters, but it is probably not as good as estimating by my method or as part of DRPM or by separate RPM factor.