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Jon Nichols
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Jose A. Martínez
Joined: 19 Jul 2009
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 Posted: Thu Nov 12, 2009 4:33 am Post subject: |
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Thank you so much Jon for this great stuff.
I have one dumb question. For example, for usage percentage, if I want to compute the percentage of plays used by a player in each game of the season, I could compute it dividing the plays of each game by the usage percentage. Correct?
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Jose A. Martínez
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Mike G
Joined: 14 Jan 2005
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Location: Hendersonville, NC
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| Posted: Thu Nov 12, 2009 5:33 am Post subject: |
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Fascinating work, Jon.
What is going on with blocks? Every player I've checked (top 20) has a lower 'true' Blk% than those listed at b-r.com | Code: | Name Team Min Blk% TBlk%
Chris Andersen DEN 1460 .093 .065
Joel Anthony MIA 1048 .072 .055
Ronny Turiaf GSW 1696 .069 .053
Theo Ratliff PHI 578 .066 .048
Dwight Howard ORL 2821 .059 .048
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The last column are the numbers on your spreadsheet. They're all 24-44% lower than B-R.com's Blk%. Similarly true for players with fewer minutes.
What kind of season totals have you gathered for these players?
And while you're recalculating stuff, how about getting 'true' TS%? Based on actual possessions used, rather than on estimate (FTA * .44).
Oh, and for some purposes it would be nice if minutes were a column. Great work.
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Mike G
Joined: 14 Jan 2005
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Location: Hendersonville, NC
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| Posted: Thu Nov 12, 2009 8:27 am Post subject: |
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Having also looked at Ast% leaders, a strong correlation between minutes played (starters) and amount overestimated. From the top 45 or so Ast% (any minutes), some teammate comparisons:
| Code: | Name Team Min Ast% TAst% ratio
Rajon Rondo BOS 2642 .397 .371 1.07
Stephon Marbury BOS 414 .266 .277 .96
Jason Kidd DAL 2886 .347 .328 1.06
Jose Barea DAL 1600 .264 .279 .95
Baron Davis LAC 2248 .381 .367 1.04
Jason Hart LAC 312 .208 .259 .80
Chris Paul NOH 3002 .545 .512 1.07
Antonio Daniels NOH 733 .283 .322 .88
Russell Westbrook OKC 2668 .275 .266 1.03
Earl Watson OKC 1776 .334 .339 .99
Tony Parker SAS 2456 .401 .379 1.06
Jacque Vaughn SAS 292 .276 .318 .87
Jose Calderon TOR 2333 .410 .406 1.01
Roko Ukic TOR 890 .272 .282 .96
Will Solomon TOR 544 .361 .367 .98
Quincy Douby TOR 73 .271 .290 .93
Marcus Banks TOR 40 .242 .273 .89
Deron Williams UTA 2505 .478 .461 1.04
Brevin Knight UTA 938 .281 .296 .95
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I'm assuming a backup is generally playing in a slower pace than that which a starter is playing.
Others for whom (estimated) Ast% seems to be at least 4% too high: LeBron, Wade, Nelson, Alston in Orl, Nash, Harris.
Are assists (and/or blocks) actually noted in the play-by-plays?
Do extras get tossed in later?
A fairly typical team breakdown (TAst% > 15) ? -
| Code: |
Phoenix Suns tm Min Ast% TAst% ratio
Steve Nash PHX 2484 .424 .406 1.04
Leandro Barbosa PHX 1705 .149 .152 .98
Goran Dragic PHX 728 .208 .237 .88
Sean Singletary PHX 122 .130 .156 .83
Dee Brown PHX 28 .131 .158 .83
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Jon Nichols
Joined: 18 Aug 2005
Posts: 370
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| Posted: Thu Nov 12, 2009 9:53 am Post subject: |
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| josean.martinez@upct.es wrote: | Thank you so much Jon for this great stuff.
I have one dumb question. For example, for usage percentage, if I want to compute the percentage of plays used by a player in each game of the season, I could compute it dividing the plays of each game by the usage percentage. Correct? |
I'm not totally sure what you're asking, but if you're asking how to estimate the number of plays a player was involved in on a game-by-game basis, you would multiply the usage rate times the fraction of minutes he was in the game times the team's pace. That would just be an estimation, though. |
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Jon Nichols
Joined: 18 Aug 2005
Posts: 370
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| Posted: Thu Nov 12, 2009 9:59 am Post subject: |
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| Mike G wrote: | Fascinating work, Jon.
What is going on with blocks? Every player I've checked (top 20) has a lower 'true' Blk% than those listed at b-r.com | Code: | Name Team Min Blk% TBlk%
Chris Andersen DEN 1460 .093 .065
Joel Anthony MIA 1048 .072 .055
Ronny Turiaf GSW 1696 .069 .053
Theo Ratliff PHI 578 .066 .048
Dwight Howard ORL 2821 .059 .048
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The last column are the numbers on your spreadsheet. They're all 24-44% lower than B-R.com's Blk%. Similarly true for players with fewer minutes.
What kind of season totals have you gathered for these players?
And while you're recalculating stuff, how about getting 'true' TS%? Based on actual possessions used, rather than on estimate (FTA * .44).
Oh, and for some purposes it would be nice if minutes were a column. Great work. |
Yes, the blocks are off, which is a bit confusing because of how easy they were to calculate. It's very easy to total the number of opposing field goal attempts while a player was on the court. The season totals I have for blocks are very slightly off, and that may be the difference. You would have to ask Ryan Parker why that is.
As for the true shot percentage, I still used the .44 estimator for free throws. I did this because I had a hard time estimating possessions that ended in free throws, because you can't simply count shooting fouls. There probably is a way to count actual possessions taking free throws into account, but this was my first go at this and I wasn't sure exactly how. Perhaps someone else could shed some light on that. |
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Jon Nichols
Joined: 18 Aug 2005
Posts: 370
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| Posted: Thu Nov 12, 2009 10:02 am Post subject: |
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| Mike G wrote: | Having also looked at Ast% leaders, a strong correlation between minutes played (starters) and amount overestimated. From the top 45 or so Ast% (any minutes), some teammate comparisons:
| Code: | Name Team Min Ast% TAst% ratio
Rajon Rondo BOS 2642 .397 .371 1.07
Stephon Marbury BOS 414 .266 .277 .96
Jason Kidd DAL 2886 .347 .328 1.06
Jose Barea DAL 1600 .264 .279 .95
Baron Davis LAC 2248 .381 .367 1.04
Jason Hart LAC 312 .208 .259 .80
Chris Paul NOH 3002 .545 .512 1.07
Antonio Daniels NOH 733 .283 .322 .88
Russell Westbrook OKC 2668 .275 .266 1.03
Earl Watson OKC 1776 .334 .339 .99
Tony Parker SAS 2456 .401 .379 1.06
Jacque Vaughn SAS 292 .276 .318 .87
Jose Calderon TOR 2333 .410 .406 1.01
Roko Ukic TOR 890 .272 .282 .96
Will Solomon TOR 544 .361 .367 .98
Quincy Douby TOR 73 .271 .290 .93
Marcus Banks TOR 40 .242 .273 .89
Deron Williams UTA 2505 .478 .461 1.04
Brevin Knight UTA 938 .281 .296 .95
|
I'm assuming a backup is generally playing in a slower pace than that which a starter is playing.
Others for whom (estimated) Ast% seems to be at least 4% too high: LeBron, Wade, Nelson, Alston in Orl, Nash, Harris.
Are assists (and/or blocks) actually noted in the play-by-plays?
Do extras get tossed in later?
A fairly typical team breakdown (TAst% > 15) ? -
| Code: |
Phoenix Suns tm Min Ast% TAst% ratio
Steve Nash PHX 2484 .424 .406 1.04
Leandro Barbosa PHX 1705 .149 .152 .98
Goran Dragic PHX 728 .208 .237 .88
Sean Singletary PHX 122 .130 .156 .83
Dee Brown PHX 28 .131 .158 .83
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Assuming it's not just an error on my part, I'm glad there are systematic differences between the estimations and the actual numbers. It shows that there's only so much the estimations can do based on box scores. As it turns out, though, they are pretty darn close.
I don't know if extra assists and blocks are tossed in later, but they are noted in the play-by-plays. Ryan's data has a column for each for each play. |
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DLew
Joined: 13 Nov 2006
Posts: 224
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| Posted: Thu Nov 12, 2009 10:24 am Post subject: |
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| Block% at basketball reference is calculated out of two point attempts (not total attemps) while the player is on the floor. I think that accounts for your discrepancy. |
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Jon Nichols
Joined: 18 Aug 2005
Posts: 370
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| Posted: Thu Nov 12, 2009 10:30 am Post subject: |
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| DLew wrote: | | Block% at basketball reference is calculated out of two point attempts (not total attemps) while the player is on the floor. I think that accounts for your discrepancy. |
Thanks. That may help explain it.
I wonder if that's an appropriate method, though. I know it's rare, but three-pointers are blocked on occasion... |
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Ryan J. Parker
Joined: 23 Mar 2007
Posts: 711
Location: Raleigh, NC
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| Posted: Thu Nov 12, 2009 10:37 am Post subject: |
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Season totals won't add up because the play-by-play isn't available for every game. The rate statistics, however, should be close.
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Jose A. Martínez
Joined: 19 Jul 2009
Posts: 72
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| Posted: Thu Nov 12, 2009 11:44 am Post subject: |
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| Quote: | | I'm not totally sure what you're asking, but if you're asking how to estimate the number of plays a player was involved in on a game-by-game basis, you would multiply the usage rate times the fraction of minutes he was in the game times the team's pace. That would just be an estimation, though. |
Thanks Jon, this is what I really wanted to know. However, I think this specific statistic is not reported in any website...or may be yes...Does anyone know if this statistic is availiable??
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Jose A. Martínez
http://www.upct.es/~beside/jose
http://basket-research.blogspot.com |
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basketballvalue
Joined: 07 Mar 2006
Posts: 208
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| Posted: Thu Nov 12, 2009 2:31 pm Post subject: |
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Nice work Jon. Have you done any assessment of the correlation between pbp calcs vs. b-r.com calcs? I'm guessing it's fairly close but clearly not exact. It'd be nice to know if it's a 1% difference, 10% difference,....
This is something that's been on my "nice to have" to do list for basketballvalue.com, but never gotten around to it. Any plans for you to update this on a regular basis?
Thanks,
Aaron
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Jon Nichols
Joined: 18 Aug 2005
Posts: 370
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| Posted: Thu Nov 12, 2009 2:58 pm Post subject: |
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I haven't done any assessments of correlation yet, but that sounds like a good idea for the future. I'll get on that shortly...
As long as I have the play-by-play data, I see no reason not to update this on a regular basis. |
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IrishHand
Joined: 15 Jul 2009
Posts: 115
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| Posted: Fri Nov 13, 2009 4:44 pm Post subject: |
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| DLew wrote: | | Block% at basketball reference is calculated out of two point attempts (not total attemps) while the player is on the floor. I think that accounts for your discrepancy. |
Really? If so, wow... |
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Jon Nichols
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