网站图文版：http://tinyurl.com/mjrfcgl : 前情提要(按)：原po这篇爆文的原文在米国也收到广大的回响 : 主要的论点就是「投射能力」应该参考「出手位置」。 : : 计算方式为找出每位球员的出手(FG)位置及次数， : 以全联盟在这些出手位置的平均，算出这些出手应当的期望得分； : ShotScore = 实际球员FG得分 - 联盟同出手位置FG期望得分 今天介绍的这篇文则对於 ShotScore 提出了三点质疑。 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? ] 有必要搞这麽复杂吗？ 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，详细的出手数据也都没有公开。 原文发表的方法是复杂中带点优雅，但谁说这统计过程的复杂是必须的？ 问题就在这其中的复杂究竟有没有带来价值。 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. 为了找出答案，我依据 BBR 站上公开的资料创造了 "effective scoring"， 只需要 球员FG 和 联盟eFG% 配上很直觉的理论和基本的数据。 (编按)ShotScore = 实际球员FG得分 - 联盟同出手位置FG期望得分 XFP = 实际球员FG得分 - 联盟同出手次数FG期望得分 = 实际球员FG得分 - (球员FGA * 联盟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 只是因为现存的得分效率指标乏善可陈(虽然真的是如此)， 那我害怕这个指标也只是用牛刀杀鸡的产物， 毕竟得分的效率其实就是「出手数*平均效率」这麽简单 [ 2. IS THERE VALUE IN BEING MORE EFFECTIVE FROM LESS EFFICIENT ZONES? ] 众人皆差我还好？ 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 鼓励的就是要在「众人皆差我还好」的地方准。 如果「右边长距离两分」在技能表里面还是相对没效率的， 那你在「右边长距离两分」比旁边那个戴眼镜的准真的有什麽价值吗？ 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 的差别就在鼓励这种「众人皆差我还好」的出手， 但实际上这些出手和进球对於球队实际的帮助不大； 人人会进的篮下是两分，个个怕放枪的长距离也是两分。 Bosh 是很会投20尺的中长距离，但DAJ的篮下摆球还是比较有效率， 所以为什麽这些出手是值得鼓励的？ 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. 你可能会说长距离比上篮、灌篮容易出手。 阿 ... 又怎麽勒？ 球队统计数据直接显示「eFG」和「长距离两分占出手比率」呈现负相关， 历史告诉我们这些出手弊多於利 (利：拉开空间、减少失误)。 所以我们为何要鼓励这类的出手呢？ 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. 况且这些对於长距离掌握度奇高的球员的确是被 ShotScore 放大， Ibaka, Horford, Bosh, Dirk 都在前十榜上有名， 而 LBJ 和 KD 则是少数榜单内以攻击篮框维生的。 另一个极端还有一份最佳三分射手榜单，包含 Korver 和 Calderon， 他们每场个别只能得11分，得分效率也比 Jordan 和 McGee 低， 但是在需要长程炮火的时候你得换上他们。 (这段有点不确定... 欢迎指正) 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. 跳投派的论点是 DAJ 一场比赛最多也就6, 7次这种篮下高效率出手， 但 Bosh却可以整晚一直长距离两分射爽爽。 换言之，要增加篮下出手数是很难的。 DAJ, McGee, Tyson 不可能每场硬是出手20球还保持良好的效率。 这是事实，但 XFP 和 ShotScore 一样都已经对少出手数不利了。 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，「接获助攻的出手」和「自己创造的出手」在这两种数据也都还没有处理， 我们都知道自干通常在某种程度上被认为是相对没效率的出手； 或许未来的 ShotScore 会考虑鼓励像是 Ellis 和 Kobe 这类创造出手机会的球员。 但回到「长距离两分」和「篮下」的比较却不能用难易之分来作为鼓励的准则， 除非你能证明简单的出手是真的有其次数的限制、真的难以被创造。 整个 2012-13 球季都依靠篮下和三分，做最有效率出手的金块就是一个例子。 [ 3. WHERE ARE THE FREE THROWS? ] 说好的罚球呢？ * 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. 除了放大了长距离射手之外， ShotScore 也忽略了常发生在篮下的犯规罚球。 忽略了罚球，我们就是在否定禁区破坏所得到的好处。 当然另一方面我们也要看把球罚进的能力，这是很多 DAJ 型球员在这点上是办不到的。 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. 另外就是忽略了罚球得分，我们也同时忽略了 NBA 球员很大部分的得分来源， KD 上一季有 30% 的分数来自於罚球线，这是我们在看得分效率上不能忽视的。 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 很容易可以带入罚球一起考虑， 我把 XFP 小小修改如下： XTP = 实际球员总得分 - 联盟同攻击次数得分 = 实际球员总得分 - (球员攻击次数 * 联盟TS% * 2) 排行图：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，怎麽会这样？ 简单说：FTM 的比项 KD 比 LBJ 多68%，KD 的 FTA 全联盟第二多，外带91%的命中率。 LBJ 虽然也很会制造犯规但还是硬生生比 KD 少了 215 次 FTA，而且只有75%的命中率。 KD 效率的惊人之处就在於创造犯规和罚进罚球的能力，而这些 ShotScore 却都忽略。 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 这个组合也是一样的道理， 火箭去年是全联盟 FTA 第一，Harden 的罚球数是 Curry 的2.7倍。(按：792比291) 虽然 Curry 罚球命中率高达90%，但罚球数远不及前三名。 也就是说 ShotScore 否定了制造犯规和罚进两罚的能力 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 的前十名榜单有五个人不同，而 XTP 专有的特色就在罚球。 ShotScore：Calderon, Horford, Bosh, Nowitzki, CP3 XTP ：Harden, Tyson, Kobe, Kevin Martin, Parker Tyson 虽然"只有"258次 FTA，但是他也只有400次的 FGA，这代表很高的制造犯规能力； 相对 Curry 的 FTA 有 291次，但 FGA 高达1388次。 (後略) 完整原文： http://tinyurl.com/mmn94rp 总结： 1. 复杂的考虑出手位置是否有其价值？ 2. 「众人皆差我还好」的出手位置为何值得鼓励？ 3. 罚球是否要纳入考虑？ 心得： 关於第三个问题或许可以说， 原设计者要比较的是「shooter」而非「scorer」， 所以并没有把罚球进算在内。 但第二个关於失传的中长距离两分球， 还真的是国内外都争论不休的一片混战。 个人认为「出手位置」的好坏不如「出手选择」的好坏， 同样的位置，有时是空档、有时是硬拔， 至少该考虑防守方的相对位置，而不只是看攻击方的出手的位置来决定。 -- ReckonBox | 睿啃盒子 算术是篮球的一部份 http://reckonbox.herokuapp.com/ --

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