站內NBA
網站圖文版：
http://tinyurl.com/mjrfcgl
: 前情提要(按)：原po這篇爆文的原文在米國也收到廣大的迴響
: 主要的論點就是「投射能力」應該參考「出手位置」。
:
: 計算方式為找出每位球員的出手(FG)位置及次數，
: 以全聯盟在這些出手位置的平均，算出這些出手應當的期望得分；
: ShotScore = 實際球員FG得分 - 聯盟同出手位置FG期望得分
今天介紹的這篇文則對於 ShotScore 提出了三點質疑。
LeBron James vs. Kevin Durant:
What matters when we assess the NBA's best scorers?
By Tom Ziller @teamziller on Oct 10 2013, 11:15a
(前略)
[ 1. IS THE COMPLEXITY NECESSARY? ]
有必要搞這麼複雜嗎？
The average Excel jockey cannot do what Goldsberry did. The detailed shot
data is not open source and the effort is, as with what most of Goldsberry
publishes, both extremely complex and elegant (a powerful combination). But
the mere fact of the statistic's complexity is not totally relevant. The
question is whether the complexity adds anything of value. (Because boy do I
know arty but extraneous complexity ...)
一般的 Excel 操作做不到原文做到的，詳細的出手數據也都沒有公開。
原文發表的方法是複雜中帶點優雅，但誰說這統計過程的複雜是必須的？
問題就在這其中的複雜究竟有沒有帶來價值。
To answer that, I went about creating my own "effective scoring" stat using
public data available at Basketball-Reference (and many other places) and a
Google Spreadsheet. (Here's that spreadsheet. Do with it what you will.) I
used straight theory and a common base stat one step up from field goal
percentage, effective field goal percentage (eFG). My formula gets each
player's number of expected points by multiplying the number of field goals
they attempted, league average eFG (.496) and two (the number of points a
made basic shot under eFG is worth). Then I subtracted their actual points
from the field (points minus made free throws) from the expected points. I
named it Extra Field Points.
為了找出答案，我依據 BBR 站上公開的資料創造了 "effective scoring"，
只需要 球員FG 和 聯盟eFG% 配上很直覺的理論和基本的數據。
(編按)ShotScore = 實際球員FG得分 - 聯盟同出手位置FG期望得分
XFP = 實際球員FG得分 - 聯盟同出手次數FG期望得分
= 實際球員FG得分 - (球員FGA * 聯盟eFG% * 2)
Goldsberry's complex creation resulted in a ShotScore top three of, in order,
LeBron (+231), Durant (+204) and Curry (+164). Here is the Extra Field Points
leaderboard.
ShotScore XFP
1. LeBron James, +231, +290
2. Kevin Durant, +204, +179
3. Stephen Curry, +164, +147
If the metric was primarily created because existing scoring effectiveness
metrics were lackluster -- and they certainly were -- then I fear that
ShotScore is the result of using the Large Hadron Collider where a bowling
ball dropped from the roof would do. Scoring effectiveness is certainly a
product of scoring production and scoring efficiency, with one big ol'
asterisk we'll talk about in Question No. 3. To remind myself of it, I'll go
ahead and put the asterisk right about here.*
如果 ShotScore 只是因為現存的得分效率指標乏善可陳(雖然真的是如此)，
那我害怕這個指標也只是用牛刀殺雞的產物，
畢竟得分的效率其實就是「出手數*平均效率」這麼簡單
[ 2. IS THERE VALUE IN BEING MORE EFFECTIVE FROM LESS EFFICIENT ZONES? ]
眾人皆差我還好？
What ShotScore does is give credit to players for being more efficient than
the average league player in the various zones of the floor that Goldsberry
has created. But is there any actual value in being a better shooter than the
next guy on 16-23 footers on the right side if that shot is still one of the
least efficient in your repertoire?
ShotScore 鼓勵的就是要在「眾人皆差我還好」的地方準。
如果「右邊長距離兩分」在技能表裡面還是相對沒效率的，
那你在「右邊長距離兩分」比旁邊那個戴眼鏡的準真的有什麼價值嗎？
What ShotScore does beyond Extra Field Points is give credit to players who
take and make shots from the less efficient spots on the floor, but there's
no actual scoring value at the team to taking and making those shots. A
two-pointer at the rim, which the average player will convert at a high rate,
is worth the same number of points as a 20-footer, which the average player
will convert at a low rate. But consider that DeAndre Jordan doesn't take
those 20-footers, he takes shots at the rim. Chris Bosh does take those
20-footers, and converts them at a high-level. But a standard DAJ at-the-rim
attempt is still more efficient than a standard Bosh 20-footer. So what's the
advantage in the 20-footer? Why give Bosh credit for taking a less efficient
shot?
ShotScore 跟 XFP 的差別就在鼓勵這種「眾人皆差我還好」的出手，
但實際上這些出手和進球對於球隊實際的幫助不大；
人人會進的籃下是兩分，個個怕放槍的長距離也是兩分。
Bosh 是很會投20呎的中長距離，但DAJ的籃下擺球還是比較有效率，
所以為什麼這些出手是值得鼓勵的？
You could argue that 20-footers are easier to get off than dunks and layups,
and you'd be right. But ... so? Data repeatedly shows a direct inverse
relationship at the team level between eFG (and/or offensive rating) and the
percentage of shots taken in the long two-pointer range. History tells us
that shooting long twos hurts a team's shooting numbers more than it might
help by opening up the floor or limiting turnovers. So why would we credit
players who take and make long twos at 50 percent at the expense of guys who
take and make shots at the rim at 70 percent? All told, that 70-percent shot
at the rim helps the team more, based on the numbers. Ten DAJ shots at the
rim will earn 14 points. Ten Bosh long twos will earn 10 points.
你可能會說長距離比上籃、灌籃容易出手。
阿 ... 又怎麼勒？
球隊統計數據直接顯示「eFG」和「長距離兩分佔出手比率」呈現負相關，
歷史告訴我們這些出手弊多於利 (利：拉開空間、減少失誤)。
所以我們為何要鼓勵這類的出手呢？
Yet this is one of the major groups of players that ShotScore elevates: the
guys who shoot long twos abnormally well (i.e. the Chris Boshes).
Goldsberry's top 10 in ShotScore includes Serge Ibaka (a 15 ppg scorer who
drains long, assisted, twos at a high rate), Al Horford, Bosh and Dirk
Nowitzki. LeBron and Durant are the only guys who live at the rim and appear
in Goldsberry's top 10 (though Ibaka, Horford and Chris Paul do damage there
as well). It is otherwise a list of the best perimeter shooters in the
league, including low-volume guys like Kyle Korver and Jose Calderon, who
each averaged about 11 points per game. You're subbing in Korver and Calderon
for Jordan and McGee on the basis that while Korver and Calderon are not more
efficient, they are doing damage further from the rim.
況且這些對於長距離掌握度奇高的球員的確是被 ShotScore 放大，
Ibaka, Horford, Bosh, Dirk 都在前十榜上有名，
而 LBJ 和 KD 則是少數榜單內以攻擊籃框維生的。
另一個極端還有一份最佳三分射手榜單，包含 Korver 和 Calderon，
他們每場個別只能得11分，得分效率也比 Jordan 和 McGee 低，
但是在需要長程砲火的時候你得換上他們。
(這段有點不確定... 歡迎指正)
The other piece of the pro-jumper argument is that, well, DAJ isn't getting
off more than six or seven high-efficiency shots at the rim per game, whereas
Bosh can get that 20-footer all night long. The capacity to expand the
paint-only player's shot frequency is highly limited. Jordan, JaVale McGee
and Tyson Chandler cannot take 20 shots per game and maintain their excellent
efficiency. That's absolute true. But Extra Field Points addresses that by
incorporating shot frequency just as ShotScore does.
跳投派的論點是 DAJ 一場比賽最多也就6, 7次這種籃下高效率出手，
但 Bosh卻可以整晚一直長距離兩分射爽爽。
換言之，要增加籃下出手數是很難的。
DAJ, McGee, Tyson 不可能每場硬是出手20球還保持良好的效率。
這是事實，但 XFP 和 ShotScore 一樣都已經對少出手數不利了。
In addition, that's a question on the value of assisted field goals and shot
creation itself, which totally isn't addressed in either stat. We know that
the unassisted shot is some degree less efficient than the assisted shot. A
future iteration of ShotScore may very well account for and give credit to
players (like Monta Ellis and Kobe Bryant) who create most of their own
shots, much as it currently gives credit to players who take less efficient
shots. But as is the case with valuing made long twos over made layups,
there's no case to be made that the more difficult shot is worth more to the
team unless you can prove that a frequency limit on easier shots exists. The
2012-13 Nuggets, for example, who lived at the rim and behind the arc taking
the most efficient shots on the floor all season long, would be the initial
counterexample to that theory that comes to mind.
另外，「接獲助攻的出手」和「自己創造的出手」在這兩種數據也都還沒有處理，
我們都知道自幹通常在某種程度上被認為是相對沒效率的出手；
或許未來的 ShotScore 會考慮鼓勵像是 Ellis 和 Kobe 這類創造出手機會的球員。
但回到「長距離兩分」和「籃下」的比較卻不能用難易之分來作為鼓勵的準則，
除非你能證明簡單的出手是真的有其次數的限制、真的難以被創造。
整個 2012-13 球季都依靠籃下和三分，做最有效率出手的金塊就是一個例子。
[ 3. WHERE ARE THE FREE THROWS? ]
說好的罰球呢？
* There's that asterisk. This is the big limit on ShotScore as it currently
exists. It leaves out a crucial piece of the scoring effectiveness puzzle.
There are two issues at play. The first is that while ShotScore credits
better perimeter shooters at the expense of the DeAndre Jordan All-Stars,
most free throws are created down where the DAJ types live and not out at the
elbows. So, by leaving out free throws, you're negating one of the crucial
benefits in having an at-the-rim game, be it at the team level or as a
personal choice. There is, of course, the caveat that you've got to be able
to draw and hit free throws. Not all DAJ types, especially the namesake, can
do those things.
除了放大了長距離射手之外， ShotScore 也忽略了常發生在籃下的犯規罰球。
忽略了罰球，我們就是在否定禁區破壞所得到的好處。
當然另一方面我們也要看把球罰進的能力，這是很多 DAJ 型球員在這點上是辦不到的。
The other issue is that when comparing the effectiveness of scorers, leaving
out free throws (both the foul-drawing aspect and the free throw shooting
aspect) you're ignoring a fat chunk of the actual scoring happening in the
NBA. About 30 percent of Kevin Durant's points last season came at the free
throw line. You can't ignore that if you're looking at overall scoring
effectiveness.
另外就是忽略了罰球得分，我們也同時忽略了 NBA 球員很大部分的得分來源，
KD 上一季有 30% 的分數來自於罰球線，這是我們在看得分效率上不能忽視的。
ShotScore could easily be upgraded with free throws in some fashion, either
just figuring in rates at which they are scored or by crediting the different
zones on the floor for fouls drawn there. Going more simply, I upgraded Extra
Field Points by tweaking the minimalist expected points formula: it's now a
player's total shooting possessions (using the standard 0.44 as the adjuster
to convert free throw attempts into shooting fouls drawn) multiplied by the
league average True Shooting percentage (.539) multiplied by two (the value
of a base shot). I subtracted that from total points scored to get Extra
Total Points. Here's the leaderboard:
ShotScore 很容易可以帶入罰球一起考慮，
我把 XFP 小小修改如下：
XTP = 實際球員總得分 - 聯盟同攻擊次數得分
= 實際球員總得分 - (球員攻擊次數 * 聯盟TS% * 2)
排行圖：http://cdn3.sbnation.com/assets/3365585/XTP-2013.png
Durant eclipses LeBron, and Harden tops Curry. How? Well, for starters,
Durant made 68 percent more free throws than LeBron. KD was No. 2 in the
league in free throw attempts and hit them at a 91 percent clip. LeBron,
though an effective foul-drawer, took far fewer FTAs than Durant (215 fewer)
and hit them at a 75 percent clip. Part of what makes Durant just an
incredibly effective scorer is his ability to draw fouls at a high rate and
convert them at such a high rate. ShotScore, it seems, ignores that.
KD 超越 LBJ，Harden 超越 Curry，怎麼會這樣？
簡單說：FTM 的比項 KD 比 LBJ 多68%，KD 的 FTA 全聯盟第二多，外帶91%的命中率。
LBJ 雖然也很會製造犯規但還是硬生生比 KD 少了 215 次 FTA，而且只有75%的命中率。
KD 效率的驚人之處就在於創造犯規和罰進罰球的能力，而這些 ShotScore 卻都忽略。
Harden over Curry is the same story: the Rocket finished No. 1 in the league
in FTAs and attempts 2.7 times as many freebies as Curry. So while Curry did
convert his free throws at a high rate (90 percent), he didn't take them
nearly as frequently as Harden, James or Durant. In leaving out a crucial
piece of scoring, ShotScore negates some of the effectiveness of guys like
Harden and Durant, who get to the line really often, and often turn those
trips into two points.
Harden 跟 Curry 這個組合也是一樣的道理，
火箭去年是全聯盟 FTA 第一，Harden 的罰球數是 Curry 的2.7倍。(按：792比291)
雖然 Curry 罰球命中率高達90%，但罰球數遠不及前三名。
也就是說 ShotScore 否定了製造犯規和罰進兩罰的能力
There are five players that the ShotScore and XTP top 10s do not have in
common. ShotScore includes Calderon, Horford, Bosh, Nowitzki and CP3. In
their places, XTP has Harden, Tyson Chandler, Kobe Bryant, Kevin Martin and
Tony Parker. The common thread among the XTP exclusives: free throws.
Chandler, for example, "only" took 258 free throws. But he did that while
taking just 400 FGAs. That's a really high rate of foul-drawing given his
shooting frequency. Curry, by comparison, took 291 FTAs and 1,388 FGAs.
ShotScore 和 XTP 的前十名榜單有五個人不同，而 XTP 專有的特色就在罰球。
ShotScore：Calderon, Horford, Bosh, Nowitzki, CP3
XTP ：Harden, Tyson, Kobe, Kevin Martin, Parker
Tyson 雖然"只有"258次 FTA，但是他也只有400次的 FGA，這代表很高的製造犯規能力；
相對 Curry 的 FTA 有 291次，但 FGA 高達1388次。
(後略)
完整原文：
http://tinyurl.com/mmn94rp
總結：
1. 複雜的考慮出手位置是否有其價值？
2. 「眾人皆差我還好」的出手位置為何值得鼓勵？
3. 罰球是否要納入考慮？
心得：
關於第三個問題或許可以說，
原設計者要比較的是「shooter」而非「scorer」，
所以並沒有把罰球進算在內。
但第二個關於失傳的中長距離兩分球，
還真的是國內外都爭論不休的一片混戰。
個人認為「出手位置」的好壞不如「出手選擇」的好壞，
同樣的位置，有時是空檔、有時是硬拔，
至少該考慮防守方的相對位置，而不只是看攻擊方的出手的位置來決定。
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※ 批踢踢實業坊(ptt.cc)※ 文章網址: https://www.ptt.cc/bbs/NBA/M.1381834810.A.CB3.html
→ kaede0711 :我覺得1,2真的是很大的爭論點,因為防守一直無法做到 10/15 19:08
→ kaede0711 :數據化,打過籃球都知道攻守是相對的,防守會影響各種 10/15 19:08
→ kaede0711 :投籃區間的比重,至於罰球就很有道理,不過我想原文可 10/15 19:10
→ kaede0711 :能是考慮到罰球是一個不可選擇的變因吧 10/15 19:10
推 a19841208 :這篇剛好補足我對原文的疑問，'像是去探討空檔出手 10/15 19:11
推 gn00945822 :推 10/15 19:12
→ a19841208 :或被防守下出手是否能數據化，太複雜計算能力質， 10/15 19:12
推 gaiaesque :防守難量化+1.. 10/15 19:13
→ kaede0711 :不過這兩篇給我的感覺比較像是在比較eFG%跟TS% 10/15 19:13
→ kaede0711 :只是多了一個"聯盟平均值"去做比較基準 10/15 19:13
→ a19841208 :卻想用一個數據表達一切，我覺得是不可能的 10/15 19:13
→ kaede0711 :自幹出手跟被助攻出手的價值衡量跟比例的確很難推算 10/15 19:15
→ kaede0711 :另外原文提到的期望值較高的籃下出手跟較低的中長距 10/15 19:15
→ kaede0711 :離出手,也沒公信的數據說一定誰難誰易 10/15 19:17
推 a19841208 :K大，文應該是說籃下比中距離好，用來反駁原文的 10/15 19:24
→ a19841208 :眾人皆差我還好]情況，所以他還加上禁區可以買犯規 10/15 19:25
→ a19841208 :情況。不過現行的SCORE可以查出手幾尺的命中率， 10/15 19:28
→ a19841208 :也相當於表示這選手的能力值和出手範圍 10/15 19:29
推 idiotsmart :推 那個論點真的還有不少缺失 不過我覺得他多少還是 10/15 19:42
→ idiotsmart :有參考價值 10/15 19:42
推 opsddb :我當初也有「眾人皆差我還好」的疑問，大量中距離出 10/15 19:48
→ opsddb :手且命中率略高於該出手位置平均值ShotScore會是正分 10/15 19:48
→ opsddb :，大量在籃下出手且命中率略低於該位置平均值的SS會 10/15 19:49
→ opsddb :是負的，但後者的得分效率實際上還是比前者好 10/15 19:50
推 opsddb :所以感覺ShotScore拿來和出手習慣類似的球員相比較恰 10/15 19:56
→ opsddb :當，畢竟是和該出手位置的聯盟平均相比 10/15 19:56
推 idiotsmart :推opsddb 這個數據比較適合跟同類型的比較 10/15 19:58
→ idiotsmart :但籃下命中率只有50%雖然比中距離45%好 卻也是沒效率 10/15 19:58
→ idiotsmart :的表徵 10/15 19:59
→ idiotsmart :就像Asik投丟很多該進的球 這對球隊的傷害也很大 10/15 20:00
推 starbury8 :內文第三點的XTP數據 看得出來KD和harden完全罰超爽 10/15 20:28
推 iamjustakid :朝聖推 10/15 20:41
推 opsddb :的確，ShotScore已經是相當有參考價值的數據了，「和 10/15 20:45
→ opsddb :相似類型球員較恰當」其實是大多數據都有的情況 10/15 20:45
推 a34567 :同樣是投進，對手的防守有沒有壓迫的價值真的大不相 10/15 20:46
→ a34567 :同 10/15 20:46
→ opsddb : 相比 10/15 20:46
→ nypgand1 :我覺得長中距離兩分的問題有些在於球員的心理弱點 10/15 21:02
→ nypgand1 :一般來說三分球硬拔的機會應該比較少 顧慮比較多 10/15 21:03
→ nypgand1 :但心裡認為兩分出手 或許就降低了出手選擇的標準 10/15 21:04
→ nypgand1 :相對之下這些長中距離的平均表現就會很差 10/15 21:04
→ nypgand1 :所以或許該控制的長中距離的出手選擇 10/15 21:05
推 jc91027557 :真希望NBA每天都有這種好文 朝聖推 10/15 21:10
→ kaede0711 :a大我了解你說的,不過我那段只是重複講一次這篇觀點 10/15 21:41
→ kaede0711 :就像O大講的,現實是,低於平均的籃下依然比高於平均的 10/15 21:41
→ kaede0711 :中長距離得分效率好,反駁者會認為,兩者的量會有差 10/15 21:42
→ kaede0711 :也就是一樣兩分,即使籃下效率好,卻無法像中長距離一 10/15 21:43
→ kaede0711 :樣因為出手容易而輕易衝高量,不過這篇也提他的觀點 10/15 21:44
→ kaede0711 :就是所謂的出手難易度,難以被證明 10/15 21:45
→ kaede0711 :這部分真的只能靠防守數據被有公信的統計出來 10/15 21:48
推 ThreeNG :推 籃球需要研發新數據 10/15 22:37
推 a34567 :如果防守真的能有效數據的話 進攻數據的準確度也能有 10/16 00:37
→ a34567 :重要突破 不過感覺是不太可能 太難量化了 10/16 00:38
推 Sephiroth :這篇只考慮到效率,如果只看效率當然只投三分跟籃下 10/16 11:42
→ Sephiroth :問題是真能那麼順利嗎? 考量到進攻打不順的時候需要 10/16 11:43
→ Sephiroth :依賴球星的單打or大個子中長距離投射,完全不同意長 10/16 11:44
→ Sephiroth :距離的2分是沒有意義的數據!這篇是建立在當攻擊方 10/16 11:44
→ Sephiroth :能選擇在哪邊出手的情況下,而不是真實比賽情況 10/16 11:45
→ Sephiroth :如果沒有進攻時間的限制,那的確除了籃下+三分空檔以 10/16 11:46
→ Sephiroth :外的出手都是沒效率且對球隊有害的 10/16 11:47
→ Sephiroth :但事實是比賽中有半數進攻都落在外圍投射,而不是輕易 10/16 11:49
→ Sephiroth :在籃框下出手 10/16 11:49
→ nypgand1 :其實他沒有否定長距離兩分 而是針對原本ShotScore 10/16 13:18
→ nypgand1 :會過於凸顯這塊區域的命中率 在做討論 10/16 13:19
推 amozartea :KD驚人的金身 10/16 17:21
