APBRmetrics

**Roland_Beech** · Joined: 14 Jan 2005 Posts: 43

so looking over the Ast'd % for players (that is the % of their own shots on which an assist was recorded), the player creating his own shot the least right now is (min 50 FGM)

98% Fred Hoiberg (52 of 53 made FG's were assisted)
90% Brent Barry
89% Greg Buckner
89% Bruce Bowen

...and at the opposite end

22% Nash
23% Francis
23% Iverson
25% Marbury

what prompted this was someone commenting on Kobe's 30% mark.

Anyway, I tried to paste in some excel data showing all players with breakouts by shot type but it doesn't format properly...can we do attachments on this forum?

I guess I'll dump it on the site:

http://www.82games.com/nbaplayerassistednumbers.xls

Ed Küpfer · Joined: 30 Dec 2004 Posts: 785 Location: Toronto

KnickerBlogger · Joined: 30 Dec 2004 Posts: 180

Ed pointed me to tabs2spaces.

Thanks to this board I can actually search & find the original post,

and the link to the software. Very nice.

Just paste excel into notepad -> select All -> Copy (to clipboard) -> Open tabs2psaces -> choose clipboard --> then paste into here -> use CODE (see above).

Much quicker to do than typing or reading that.

Kevin Pelton · Posted: Fri Jan 14, 2005 4:57 pm Post subject:

Early last season, I typed in all the assisted field goal percentages and tried to come up with a relatively simple formula to predict it (Dean has his own, but I'm pretty sure it's a lot more complicated).

I came up with the following:

aFG% = .42 - .63*assist share - .89*(FTA/Min) + 2/3*(team aFG%)

(assist share is the estimated percentage of assists a player is responsible for when he's on the floor -- this is to reflect the fact that you can't assist yourself)

Here are my estimates for Roland's top and bottom players:

Ed Küpfer · Joined: 30 Dec 2004 Posts: 785 Location: Toronto

Here's Roland's data, with players <20 FGM removed, shown in a boxplot.

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ed

Kevin Pelton · Posted: Mon Jan 17, 2005 9:07 pm Post subject:

After poking around the data a bit, I've come up with a vastly improved formula:

aFG%/tmaFG% = 1.53 - 1.442*assist share -.041*Oreb/48 - .787*Ps% + .014*Spec

This now predicts the ratio of a player's assisted field goal percentage and his team's overall percentage with an r^2 of .566.

The key was coming up with the three-point specialist rating. I settled on (3A/FGA)^2 * (1/Ps%)^2. The less often you shoot, and the more often you shoot threes, the more of a three-point specialist you are. This fixes much of the problem I was having with underrated the assisted percentage of these guys:

Ed Küpfer · Joined: 30 Dec 2004 Posts: 785 Location: Toronto

Kevin Pelton · Posted: Mon Jan 17, 2005 9:34 pm Post subject:

Possession percentage (which in this case is actually represented as from zero to one, thus making it not a percentage, but whatever).

Ed Küpfer · Joined: 30 Dec 2004 Posts: 785 Location: Toronto

If you want to try the 03-04 numbers, I have them here. Else, I'll give it a shot tomorrow.
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ed

Mike G · Posted: Mon Aug 07, 2006 6:26 am Post subject:

Kevin Pelton · Posted: Mon Aug 07, 2006 10:04 am Post subject:

Mike G · Posted: Wed Oct 04, 2006 9:44 am Post subject:

OK, only a couple of months later I've got a maybe decent estimator of Unassisted-FG %. That is to say, the % of a player's FG (made) which were unassisted:

uAst% = FTA*.50 + OReb*.34 + Ast*1.64 + Stl*2.27 + TO*2.78 - (3FG/FG)*.127

All these terms are per-minute, excepting the final one, the % of a player's FG which were 3's.
I have no idea why steals and turnovers correlate positively with shot-creation; perhaps they're all indicators of 'independence' on the court.

Here's a comparison of Estimated uAst% and actual, for the top 15 FG-makers in the league last year; in order of 'error' (overestimation):

Mike G · Posted: Wed Oct 04, 2006 10:56 am Post subject:

Using the formula explained above, here are comparisons with uAst% for the lowest 15 players in the league in that measure. (From among 285 players who made at least 100 FG):