page 1 of 1
Author Message
Levy2725
Joined: 07 Aug 2010
Posts: 8
Location: Boise
PostPosted: Fri Mar 25, 2011 10:49 am Post subject: Questions about Individual Defensive Rating Reply with quote
I had some questions about Dean Oliver's Individual Defensive Rating that I was hoping someone could help clarify for me. I wrote a piece for the The Two Man Game yesterday looking at how Corey Brewer measures out on some of the available defensive metrics. I classified Individual Defensive Rating as a statistic derived from play-by-play data. Greyberger, a freqeuent commenter here, said that he thought the metric was derived from box score statistics.
I went back and re-read the chapter in Oliver's book this morning. I may be having some problems with my functional reading comprehension because I'm still confused. I couldn't find an explicit characterization of the statistics as either box score or play-by-play based. However, in my limited understanding some of the formula components seem like they could only come from play-by-play data. These were the three in particular which stood out to me:
-%TeamDPossessions, the percentage of a team's defensive possessions faced by a player
-DPtsPerScPoss, Points allowed per scoring possession by a defender
-Stop%, the percentage of possessions on which the defender stops their opponent from scoring
Again, I'm still learning about all of this stuff, but I'm not sure how any of those could be derived from box score statistics.
Oliver does reference using box score statistics later in the chapter but my understanding was that they were used to modify and refine Individual Defensive Rating after it had already been calculated by the formula he layed out earlier in the chapter.
The only place I know that has Individual Defensive Rating available is Basketball-Reference. Does anyone know what source data they use to calculate the ratings? Any idea on whether they use the box score modifications Oliver discusses? Any thoughts on the characterization of this metric as box score based/play-by-play based or some other option?
Thanks so much!
_________________
Hickory-High.com
Back to top
View user's profile Send private message Visit poster's website
deepak
Joined: 26 Apr 2006
Posts: 665
PostPosted: Fri Mar 25, 2011 11:33 am Post subject: Reply with quote
It is calculated/estimated from the boxscore, not the play-by-play.
The formulas, in full detail, are in the appendix of Basketball on Paper as I recall.
Back to top
View user's profile Send private message
Levy2725
Joined: 07 Aug 2010
Posts: 8
Location: Boise
PostPosted: Fri Mar 25, 2011 12:30 pm Post subject: Reply with quote
Thanks Deepak. I re-read the appendix. If I've got it right those three components I pulled out are not actually calculated (because of a lack of source data) but are approximated based on box-score data.
Does anyone know if Basketball-Reference does the games played/minutes played and team FG% by position modifications that Oliver brings up?
_________________
Hickory-High.com
Back to top
View user's profile Send private message Visit poster's website
Kevin Pelton
Site Admin
Joined: 30 Dec 2004
Posts: 979
Location: Seattle
PostPosted: Fri Mar 25, 2011 12:53 pm Post subject: Reply with quote
The way Defensive Rating is built, it could be applied to play-by-play data (along the lines of how DeanO uses defensive tracking numbers in Basketball on Paper), but in practice, yes, it's built from the box score.
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Ilardi
Joined: 15 May 2008
Posts: 265
Location: Lawrence, KS
PostPosted: Fri Mar 25, 2011 1:01 pm Post subject: Reply with quote
Kevin Pelton wrote:
The way Defensive Rating is built, it could be applied to play-by-play data (along the lines of how DeanO uses defensive tracking numbers in Basketball on Paper), but in practice, yes, it's built from the box score.
Can someone give the actual formula here?
Back to top
View user's profile Send private message
Levy2725
Joined: 07 Aug 2010
Posts: 8
Location: Boise
PostPosted: Fri Mar 25, 2011 1:14 pm Post subject: Reply with quote
DRtg=TeamDRtg. + %TeamDPoss x (100 x DPtsScPoss x (1-Stop%) - TeamDRtg.
The explanations for %TeamDPoss, DPtsScPoss and Stop% are in my initial post
Does anyone know of someone with a system for running these calculations off PbP data?
_________________
Hickory-High.com
Back to top
View user's profile Send private message Visit poster's website
bbstats
Joined: 25 Apr 2010
Posts: 46
PostPosted: Fri Mar 25, 2011 1:47 pm Post subject: Reply with quote
Shameless plug:
Rather than estimating that all stops are equal to 'zero', I have separated 0,1,2, and 3 point possessions in my own version of Defensive Rating found here.
EDIT: Here are the results as of February-ish in the NBA.
_________________
http://thebasketballdistribution.blogspot.com
http://twitter.com/bbstats
Back to top
View user's profile Send private message Visit poster's website
Ryan J. Parker
Joined: 23 Mar 2007
Posts: 711
Location: Raleigh, NC
PostPosted: Fri Mar 25, 2011 4:11 pm Post subject: Reply with quote
You might find this interesting, although the formulas I used were just worked from what's in BoP:
http://www.basketballgeek.com/2009/10/3 ... play-data/