Comparing the contribution of NBA draft picks（转）

When it comes to the NBA draft, experts tend to argue about a number of things: at which position will a player be selected? what is the best draft class ever? etc… Luckily, the wealth of data made available by the great people ofhttp://www.basketball-reference.com/draft/ make it possible to address a number of these, and other questions.

To begin, I started off by writing a quick Python script to scrape draft data for the time period of 1980-2014 (see at the end of this post for the source code, or on my GitHub). For the purpose of this analysis, I focussed on some key metrics that I deemed to be informative and useful enough to investigate further, which included:

• Name of player (player)
• College of drafted player (college)
• Year of draft (draft_year)
• Draft pick rank (rank)
• Team that drafter the player (team)
• Total games played (gp)
• Total minutes played (mp)
• Minutes per game (mpg)
• Points per game (ppg)
• Assists per game (apg)
• Rebounds per game (rbg)
• Win shares (ws)
• Win shares per 48 minutes (ws_48)
• Total years in league (yrs)

Once this was achieved, I began by measuring the respective contribution of each pick position during the period of 1980-2014. Here, I simply computed and normalized the median statistics for each pick position. Not too surprisingly, higher draft picks tend to be contribute more to their respective teams, although we do notice that some late 2nd round draft pick have high win shares per 48 numbers. It turns out that these correspond to the picks at which Kurt Rambis (57th) and Manu Ginobilli (58th) were picked…but more on this later

Next, I decided to estimate the quality of each draft year by measuring how players performed in comparison to players picked at the same rank during other years. I was somewhat surprised to discover that the draft crop of 2008 was the one with the highest win shares, although looking back at the players that participated at that draft,it makes a lot of sense! On the other hand, the vaunted draft class of 1984 (Olajuwon, Barkley, Jordan) and 2003 (James, Anthony, Wade, Bosh) did not fare as well, which may be attributable to the fact that these included more elite players, but were far less deep in the lower picks of the draft.

Next, I looked at the longevity of each draft pick, in other words how long each draft pick is expected to remain in the NBA league, which can be achieved by using survival curves. Not too surprisingly, higher draft picks are much more likely to stay longer in the league. As a general observation, this also means that NBA teams are quite proficient at selecting the right players at the right position.

At this point, we can examine the relative performance of NBA teams with regards to their drafting skills. To do this, I compared the performance of each player compared to the average performance of other players drafted at the same position, computed the respective ratios, and summed these up for each NBA team. This analysis revealed that the top 5 drafting teams were Detroit Pistons, Cleveland Cavaliers, Memphis Grizzlies, Phoenix Suns and the San Antonio Spurs (I purposely ignored the Brooklyn Nets and the New Orleans Hornets because of the small number of years these two teams have been in the league.)

Finally, I decided to look for the best players picked at each position. Again, I compared each player’s career stats to the average numbers obtained by other players picked at the same position. For display purposes, I only show the top three players at each pick position, although you can easily reproduce the results by re-running my code here. (At this point, I should take the opportunity to advertise the great stargazerR package, which allows to quickly output R objects into LaTex or HTML tables). The results I obtained made a lot of sense, and I was very interested to learn that even at pick position 13, Kobe Bryant was only the 2nd best pick, as he was outnumbered by none other than the Mailman himself (i.e. Karl Malone). Of course, this analysis only considers numbers as opposed to achievements and trophies, but I think it is still amusing to find that Kobe Bryant isn’t even the most productive player at his position.

	Best pick	2nd best pick	3rd best pick
1	LeBron James	John Wall	Allen Iverson
2	Isiah Thomas	Jason Kidd	Gary Payton
3	Michael Jordan	Deron Williams	Pau Gasol
4	Chris Paul	Russell Westbrook	Stephon Marbury
5	Charles Barkley	Dwyane Wade	Kevin Garnett
6	Damian Lillard	Brandon Roy	Antoine Walker
7	Kevin Johnson	Stephen Curry	Alvin Robertson
8	Andre Miller	Clark Kellogg	Detlef Schrempf
9	Dirk Nowitzki	Tracy McGrady	Andre Iguodala
10	Paul Pierce	Brandon Jennings	Paul George
11	Fat Lever	Michael Carter-Williams	Terrell Brandon
12	Mookie Blaylock	Muggsy Bogues	John Bagley
13	Karl Malone	Kobe Bryant	Sleepy Floyd
14	Tim Hardaway	Clyde Drexler	Peja Stojakovic
15	Steve Nash	Al Jefferson	Gary Grant
16	John Stockton	Nikola Vucevic	Metta World Peace
17	Jrue Holiday	Josh Smith	Shawn Kemp
18	Mark Jackson	Ty Lawson	Joe Dumars
19	Rod Strickland	Zach Randolph	Jeff Teague
20	Larry Nance	Jameer Nelson	Paul Pressey
21	Rajon Rondo	Darren Collison	Michael Finley
22	Scott Skiles	Reggie Lewis	Kenneth Faried
23	Tayshaun Prince	A.C. Green	Wilson Chandler
24	Sam Cassell	Kyle Lowry	Arvydas Sabonis
25	Jeff Ruland	Mark Price	Nicolas Batum
26	Vlade Divac	Kevin Martin	George Hill
27	Dennis Rodman	Jamaal Tinsley	Jordan Crawford
28	Tony Parker	Sherman Douglas	Gene Banks
29	Toni Kukoc	Josh Howard	P.J. Brown
30	Gilbert Arenas	Nate McMillan	David Lee
31	Doc Rivers	Danny Ainge	Nikola Pekovic
32	Rashard Lewis	Brent Price	Luke Walton
33	Grant Long	Dirk Minniefield	Steve Colter
34	Carlos Boozer	Mario Chalmers	C.J. Miles
35	Mike Iuzzolino	DeAndre Jordan	Derek Smith
36	Clifford Robinson	Ersan Ilyasova	Omer Asik
37	Nick Van Exel	Mehmet Okur	Jeff McInnis
38	Chandler Parsons	Chris Duhon	Steve Blake
39	Rafer Alston	Earl Watson	Khris Middleton
40	Monta Ellis	Dino Radja	Lance Stephenson
41	Cuttino Mobley	Popeye Jones	Otis Smith
42	Stephen Jackson	Patrick Beverley	Matt Geiger
43	Michael Redd	Eric Snow	Trevor Ariza
44	Chase Budinger	Malik Rose	Cedric Henderson
45	Goran Dragic	Hot Rod Williams	Antonio Davis
46	Jeff Hornacek	Jerome Kersey	Voshon Lenard
47	Paul Millsap	Mo Williams	Gerald Wilkins
48	Marc Gasol	Micheal Williams	Cedric Ceballos
49	Andray Blatche	Haywoode Workman	Kyle O’Quinn
50	Ryan Gomes	Paul Thompson	Lavoy Allen
51	Kyle Korver	Jim Petersen	Lawrence Funderburke
52	Fred Hoiberg	Anthony Goldwire	Lowes Moore
53	Anthony Mason	Tod Murphy	Greg Buckner
54	Sam Mitchell	Shandon Anderson	Mark Blount
55	Luis Scola	Kenny Gattison	Patrick Mills
56	Ramon Sessions	Amir Johnson	Joe Kopicki
57	Manu Ginobili	Marcin Gortat	Frank Brickowski
58	Kurt Rambis	Don Reid	Robbie Hummel
59	NA	NA	NA
60	Isaiah Thomas	Drazen Petrovic	Robert Sacre

As usual, all the code for this analysis can be found on GitHub account.

CAVEATS

With regards to the analysis shown above, it is important to highlight a few potential caveats:

• I worked with career averages, which somewhat ignores the years of peak performance achieved by certain players. However, I feel it that career averages are a reasonably good proxy for overall player competence.
• I completely ignored the fact that some teams had more opportunities to select higher draft picks than others (cough…Cleveland…cough). As such, there may be a bias towards historically bad teams that would have been in the top 5 picks more often than others. However, I did compare each player to others that were picked at the same position, some hopefully this will bypass the issue (for example, if a team had plenty of NO 1 picks that were bad compared to other NO 1 picks, this insight will be revealed in the analysis)

转自：https://statofmind.wordpress.com/2015/01/26/comparing-the-contribution-of-nba-draft-picks/