标题类别想了好久，应该算是外絮，但是引用两篇文章
反正都是在讨论 真实正负值(RPM: real plus minus)
所以用专栏来定义好了 @@
原文：
http://espn.go.com/nba/story/_/id/10740818/introducing-real-plus-minus
数据：
http://espn.go.com/nba/statistics/rpm/_/sort/RPM
Bulls coach Tom Thibodeau recently made the case for Taj Gibson as
the NBA's Sixth Man of the Year. "I think that the biggest thing
for him is what he has contributed to us winning," said Thibs.
"The things that he does for us are all team-oriented. He plays
great defense, challenges shots, guards everybody, runs the floor
hard, sets great screens, does his job."
公牛教头锡伯杜最近认为手下悍将Taj Gibson应该要被
考虑为最佳第六人。“我认为最重要的是-他做了很多帮我们赢球的事，
大部份的事情都是用整体来看才看得出来的。他防守，干扰投篮，
守五个位置，在场上尽力奔跑，做出漂亮的单档，做好该做的事。”
So Gibson helps his team win by doing all the little things that
never show up in a box score. But how can we measure the value of
running the floor hard, or making smart defensive rotations, or
setting great screens?
简单来说，Gibson在场上做了一堆不会在分数盒中列出的小事
帮助球队赢球。我们要用什么方式来显示出这种贡献呢？
And how can we tell if Gibson has been more valuable to his team
than, let's say, Clippers sixth man Jamal Crawford, who has scored
more points than Gibson (18.6 versus 13.2 PPG) on a higher true
shooting percentage (55.7 versus 52.8) while logging heavier
minutes (30.3 versus 28.8 MPG) for a better team in a tougher
conference?
而且我们要怎样才能比较出来Gibson比快艇的最佳第六人Jamal Crawford
还更有价值呢？Crawford比Gibson更能得分（18.6ppg vs 13.2ppg），
而且投篮也更精准（真实命中率 55.7% vs 52.8%)，上场时间也更多
（30.3mpg vs 28.8mpg)，并且在比较强的球队和比较艰难的西区？
Today we're introducing an advanced metric that can help us out:
real plus-minus (RPM).
今天我要向大家介绍ESPN一个新的进阶数据来帮助我们：
真实正负值（RPM)。
What is real plus-minus?
什么是RPM？
As the name suggests, real plus-minus shares a family resemblance
with the +/- stat in the box score, which merely registers the net
change in score (plus or minus) while each player is on the
court.
就如同名字所叙，RPM跟分数盒上的 +/-值是属于同一家族的。
然而一般+/-值代表的只是单纯的该球员在场上球队的胜分或负分差。
RPM is inspired by the same underlying +/- logic: If a team
outscores its opponents when a player is on the court, he's
probably doing something to help his team, whether or not he's
putting up big numbers.
RPM是利用与此相同的概念-当一个球员在场上时对球队的整体帮助
而不论他个人表现与否。
But the familiar +/- stat has a serious flaw: Each player's rating
is heavily influenced by the play of his on-court teammates.
但是睿智的乡民都知道一般+/-值有着严重的缺失：
会大幅度受到跟你一起上场球员的影响。
For example, in the basic +/- numbers, Thunder backup point guard
Reggie Jackson is ranked 27th in the league. But he's also spent
the majority of his minutes playing alongside Kevin Durant, the
league's likely MVP. What we really want to know is how much of
Jackson's elite rating is attributable to his own play, and basic
+/- simply can't tell us.
举例来说，如果只看一般的+/-值，你会发现雷霆的替补控卫
Reggie Jackson在联盟能排到第27位！但是他大部份上场的时间都是
和今年最有可能的MVP-Kevin Durant一起。我们真正想要知道的是，
这个+/-有多少能看成是Jackson自己的功劳，而不是靠KD，而一般的
+/-值并不能告诉我们这一点。
But real plus-minus can.
但是真实正负值可以。
Where does real plus-minus come from?
RPM是从哪来的咧？
Drawing on advanced statistical modeling techniques (and the
analytical wizardry of RPM developer Jeremias Engelmann, formerly
of the Phoenix Suns), the metric isolates the unique plus-minus
impact of each NBA player by adjusting for the effects of each
teammate, opposing player and coach.
从进阶的数据分析技术而来（分析师Jeremias Engelmann），
这个分析把队友，对手和教练的影响考量进去，
把个别NBA球员的正负影响分离出来。
The RPM model sifts through more than 230,000 possessions each NBA
season to tease apart the "real" plus-minus effects attributable
to each player, employing techniques similar to those used by
scientific researchers when they need to model the effects of
numerous variables at the same time.
RPM模型是利用NBA每一季超过23万次球权来分析有多少+/-属于
个别球员的贡献。这里运用的运算技术和科学研究上常常要用来
分析多种变异值是类似的。
RPM estimates how many points each player adds or subtracts, on
average, to his team's net scoring margin for each 100 possessions
played. The RPM model also yields separate ratings for the
player's impact on both ends of the court: offensive RPM (ORPM)
and defensive RPM (DRPM).
简单来说，RPM预计该球员上场时，平均能为球队在100次球权
中带来多少的正负变化。因此，RPM可以更细分为防守RPM(DRPM)和进攻RPM
(ORPM）。
So, Gibson or Crawford?
所以，是Gibson还是Crawford强？
Let's return to the previous comparison of Taj Gibson and Jamal
Crawford. The chart shows their respective RPM ratings.
让我们回到Gibson vs Crawford的问题上。看看下表。
REAL PLUS-MINUS (2013-14)
PLAYER ORPM DRPM RPM
T. Gibson 0.70 3.42 4.12
J. Crawford 1.53 -1.96 -0.43
Crawford has the higher
offensive RPM (+1.53 versus +0.70), but the advantage turns out to
be surprisingly small, given Crawford's scoring talents. It's
worth only about one additional point per game.
Crawford有着更高的ORPM，但是差别比想像中小，尤其如果
考量Crawford是个抢分高手。但是Crawford只勉强比Gibson多一分。
And on the other end, the players are miles apart. In fact,
Gibson's defensive impact (+3.42 DRPM) is large enough to give him
a truly elite overall RPM rating (+4.12), placing him in the
company of All-Stars like James Harden (+3.44 RPM), Chris Bosh
(+3.75), Joakim Noah (+3.89), Russell Westbrook (+4.09) and Dwight
Howard (+3.99).
另一方面，两个球员相差就不可以道里计了。
事实上，Gibson的防守影响让他的整体RPM(+4.12)甚至可以和全明星
James Harden(+3,44), Bosh (+3.75), Noah (+3.89), 西河(+4.09)
DH12 (+3.99)相提并论。
In contrast, Crawford appears to give away a bit more on defense
(-1.96 DRPM) than he contributes on offense, with an overall RPM
impact (-0.43) that's slightly below the league average.
相反的，Crawford在防守端成为球队的负担（-1.96)，
这甚至让他的整体RPM(-0.43)略低于联盟平均(0)。
The Durant factor
Durant效应
RPM can also shed light on our question about the true impact of
third-year guard Reggie Jackson, as the table shows.
RPM也可以让我们知道前面所说的Jackson对球队的真实影响力。
REAL PLUS-MINUS (2013-14)
PLAYER ORPM DRPM RPM
K. Durant 6.10 0.67 6.77
R. Westbrook 4.08 0.01 4.09
S. Ibaka 0.47 2.63 3.10
R. Jackson 0.67 0.82 1.49
RPM accounts for the contributions of OKC stars Durant, Russell
Westbrook and Serge Ibaka (as well as Jackson's other teammates).
RPM会考量OKC其他队友的贡献来作修整。
After doing so, RPM indicates Jackson has had a moderately
positive impact this season on both sides of the ball. His total
RPM rating (+1.49), while far below that of his more heralded
teammates, is consistent with the play of a quality NBA starter,
and it's higher than that of more established guards such as Lance
Stephenson, Kevin Martin and Wesley Matthews.
在修整后，我们看出Jackson的确也还维持着正面的影响(+1.49)，
但是跟他的明星队友比就还是差了一个档次，基本上这说明他足以担当
合格的先发，他的RPM比Lance Stephenson, Kevin Martin和Wesley Mattews
都还高。
The King of RPM?
RPM的王？
Let's close with a quick look at the game's greatest all-around
player, LeBron James.
让我们回头来看看NBA里最全能的球员Lebron James。
LeBron has been accused of coasting at times this season, and RPM
reveals where the charge may have merit.
Lebron本季被外界说常常养身，让我们用RPM来看看
这个指控是否成立。
REAL PLUS-MINUS (2013-14)
PLAYER ORPM DRPM RPM
L. James 8.32 -0.21 8.11
While LeBron was aptly named to the NBA All-Defensive Team last
season, his defensive impact this season has been surprisingly
mediocre, at least as measured by RPM (-0.21 DRPM). His rating is
consistent with the claim that James has not consistently given
his best effort this season on the defensive end.
去年Lebron毫无疑问的入选ＮＢＡ防守第一队，
今年他在防守端的表现却非常一般，甚至对球队带来些微负面的影响(-0.21)。
这让那些指控他在防守端上未尽全力的看法不谋而合。
Does the same hold true on offense? No. Offensively LeBron has
been as dominant as ever, and his +8.32 ORPM leads the league by a
comfortable margin. This means that despite his less-than-stellar
defensive contribution, LeBron's total RPM (+8.11) still rates as
the NBA's highest this season.
不过在进攻端上是否也是如此呢？不。
进攻端上Lebron还是很有统治力。他的ORPM(+8.32)领先联盟其他人
不止一个档次。事实上，这样的领先让他即使扣掉他不及格的DRPM后，
整体RPM(+8.11)依然是联盟最高。
Of course, that doesn't necessarily mean he should be regarded as
the league's MVP. There's a certain prolific scorer in OKC who has
also put up a stellar RPM number this season, and he's done so
while playing more possessions than LeBron.
当然，这不代表他就应该夺得联盟的MVP了。因为在雷霆的那位
也不是吃素的，同样有着相当高的RPM，并且他进攻和防守的球权次数
也比Lebron更高。
Later this week we'll look at how RPM can be used to estimate the
number of wins each player adds to his team. In other words, we'll
introduce a new lens through which to view this season's MVP
race. (Spoiler alert: It's close. Very close.)
接下来我们将会用这项新的数据来帮我们预测哪个球员
对他的球队提供了最多胜利。也就是说，我们用一种新的方向
和思维去看本季MVP应该奖落谁家。（爆雷：比数很接近，非常接近。）
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说实话这篇叙述文没有提到任何公式，还满难看懂是怎么算的。
不过提到这个改良版的+/-有考量一起上场的队友因素和球队胜败因素等等
不管怎样应该是比传统+/-值有参考价值?