- [A veritable posting explosion from your usually lurking author...]

Speaking of goofy ratings...

Whenever I look at a boxscore, I've always subtracted misses from points. It just seems

like an easy way to mentally calculate scoring efficiency. Recently, I decided to

formalise the calculations, and give it a little stronger theoretical basis. This is

what I came up with:

Efficiency Points = pts + 1*(2pointers made) - 1*(2pointers missed)

+ 2*(3pointers made) - 1*(3pointers missed)

+ 0.5*(free throws made) - 0.5*(FT missed)

- 1*(turnovers) + 1*(offensive rebounds)

The assumption is this: teams generally average pretty close to 1 point per possession.

That means that whenever a player ends a possession without scoring, he "costs" his

team 1 point -- the point his team could normally expect. A missed 3 pointer ends a

possession with zero points -- as does a missed 2 -- so that player has 1 EffPT

subtracted from his total. Similarly, a turnover ends a possession with zero points,

and the player will be docked 1 EffPT for each one.

On the other hand, a made 2 pointer gives a team 1 point more the

expected-one-point-per-possession. That extra point gets added to that players total. A

trey is 2 points more than the expected.

Offensive rebounds take a zero-point possession, and turn it into a normal

expected-one-point-possession. One EffPT goes to that player.

The free throws get a 0.5 coefficient, for purely arbitrary reasons. I can't figure out

how much they are actually worth, or even conceive of a way to calculate it.

Assists are not included because there's no easy way to deduct the EffPTS from the

assistee. This, I think, limits the usefulness of the rating.

That's all there is to it. As an example, here's the box of tonight's Rap-Bucks game.

EffPts are in parentheses.

Bucks 95, Raptors 98

2/4/2003 Bradley Center, Milwaukee, WI

Raptors

PLAYER POS MIN FGM-A 3GM-A FTM-A OFF AST TO PTS EffPTS

VINCE CARTER G 34 11-24 1-3 2-2 2 4 0 25 [27]

ALVIN WILLIAMS G 34 5-12 1-2 0-2 0 2 2 11 [7]

JEROME WILLIAMS F 39 5-7 0-0 3-6 4 1 1 13 [19]

MORRIS PETERSON F 27 6-9 1-2 1-3 2 1 1 14 [19]

ANTONIO DAVIS C 44 7-13 0-0 2-2 7 3 3 16 [22]

Voshon Lenard 35 3-12 1-3 6-7 2 2 2 13 [11]

Rafer Alston 14 2-5 0-2 0-0 0 3 2 4 [1]

Michael Bradley 13 1-1 0-0 0-0 1 1 2 2 [2]

TOTAL 240 40-83 4-12 14-22 18 17 13 98 [107]

Bucks

PLAYER POS MIN FGM-A 3GM-A FTM-A OFF AST TO PTS

SAM CASSELL G 39 8-14 1-1 3-4 2 7 2 20 [24]

RAY ALLEN G 35 9-17 3-7 0-0 1 3 2 21 [24]

ANTHONY MASON F 36 5-13 0-0 3-4 1 7 2 13 [10]

TIM THOMAS F 21 1-6 0-1 0-0 0 0 3 2 [-5]

ERVIN JOHNSON C 25 0-2 0-0 0-0 6 0 2 0 [2]

Michael Redd 30 10-14 2-5 2-2 1 0 1 24 [33]

Toni Kukoc 20 2-5 1-3 2-2 0 2 2 7 [6]

Kevin Ollie 18 0-4 0-0 0-0 0 0 0 0 [-4]

Jason Caffey 16 4-6 0-0 0-0 2 1 1 8 [11]

TOTAL 240 39-81 7-17 10-12 13 20 15 95 [101]

Note that EffPTS don't add up exactly to actual points. I've run this test on about a

dozen games so far, and while they never seem to add up exactly, EffPTS is almost

always within 10 points of the actual total, usually overestimating. Considering the

shaky basis of my assumptions, I think that's pretty good -- although I'd like to get

it closer. The one rule I gave myself: I'm not allowed to change any of the weights,

except for free throws. I still have no idea how much they are worth with regards to

possessions. Anybody have any ideas?

ed - Ed --

Take a look back at Message 14. That message discusses some of the

other methods for weighting stats. JohnH of this group wrote a book

with different weights. There is an economist named Dave Berri who

also has something effectively similar. There are a few more on the

web, too. I've developed a matrix showing the relative weights that

the developers put on the different stats. I can't put that matrix

out here since it's in the book I've got coming out.

Yours is slightly different, of course, because you don't include any

defensive stats, making it purely an offensive tool. That makes it

somewhat unique.

DeanO

--- In APBR_analysis@yahoogroups.com, <igorkupfer@r...> wrote:

> [A veritable posting explosion from your usually lurking author...]

>

> Speaking of goofy ratings...

>

> Whenever I look at a boxscore, I've always subtracted misses from

points. It just seems

> like an easy way to mentally calculate scoring efficiency.

Recently, I decided to

> formalise the calculations, and give it a little stronger

theoretical basis. This is

> what I came up with:

>

> Efficiency Points = pts + 1*(2pointers made) - 1*(2pointers missed)

> + 2*(3pointers made) - 1*(3pointers missed)

> + 0.5*(free throws made) - 0.5*(FT missed)

> - 1*(turnovers) + 1*(offensive rebounds)

>

> The assumption is this: teams generally average pretty close to 1

point per possession.

> That means that whenever a player ends a possession without

scoring, he "costs" his

> team 1 point -- the point his team could normally expect. A missed

3 pointer ends a

> possession with zero points -- as does a missed 2 -- so that player

has 1 EffPT

> subtracted from his total. Similarly, a turnover ends a possession

with zero points,

> and the player will be docked 1 EffPT for each one.

>

> On the other hand, a made 2 pointer gives a team 1 point more the

> expected-one-point-per-possession. That extra point gets added to

that players total. A

> trey is 2 points more than the expected.

>

> Offensive rebounds take a zero-point possession, and turn it into a

normal

> expected-one-point-possession. One EffPT goes to that player.

>

> The free throws get a 0.5 coefficient, for purely arbitrary

reasons. I can't figure out

> how much they are actually worth, or even conceive of a way to

calculate it.

>

> Assists are not included because there's no easy way to deduct the

EffPTS from the

> assistee. This, I think, limits the usefulness of the rating.

>

> That's all there is to it. As an example, here's the box of

tonight's Rap-Bucks game.

> EffPts are in parentheses.

>

> Bucks 95, Raptors 98

> 2/4/2003 Bradley Center, Milwaukee, WI

>

> Raptors

>

> PLAYER POS MIN FGM-A 3GM-A FTM-A OFF AST TO PTS

EffPTS

> VINCE CARTER G 34 11-24 1-3 2-2 2 4 0

25 [27]

> ALVIN WILLIAMS G 34 5-12 1-2 0-2 0 2 2

11 [7]

> JEROME WILLIAMS F 39 5-7 0-0 3-6 4 1 1

13 [19]

> MORRIS PETERSON F 27 6-9 1-2 1-3 2 1 1

14 [19]

> ANTONIO DAVIS C 44 7-13 0-0 2-2 7 3 3

16 [22]

> Voshon Lenard 35 3-12 1-3 6-7 2 2 2

13 [11]

> Rafer Alston 14 2-5 0-2 0-0 0 3 2

4 [1]

> Michael Bradley 13 1-1 0-0 0-0 1 1 2

2 [2]

>

> TOTAL 240 40-83 4-12 14-22 18 17 13

98 [107]

>

>

> Bucks

>

> PLAYER POS MIN FGM-A 3GM-A FTM-A OFF AST TO PTS

> SAM CASSELL G 39 8-14 1-1 3-4 2 7 2

20 [24]

> RAY ALLEN G 35 9-17 3-7 0-0 1 3 2

21 [24]

> ANTHONY MASON F 36 5-13 0-0 3-4 1 7 2

13 [10]

> TIM THOMAS F 21 1-6 0-1 0-0 0 0 3

2 [-5]

> ERVIN JOHNSON C 25 0-2 0-0 0-0 6 0 2

0 [2]

> Michael Redd 30 10-14 2-5 2-2 1 0 1

24 [33]

> Toni Kukoc 20 2-5 1-3 2-2 0 2 2

7 [6]

> Kevin Ollie 18 0-4 0-0 0-0 0 0 0

0 [-4]

> Jason Caffey 16 4-6 0-0 0-0 2 1 1

8 [11]

>

> TOTAL 240 39-81 7-17 10-12 13 20 15

95 [101]

>

> Note that EffPTS don't add up exactly to actual points. I've run

this test on about a

> dozen games so far, and while they never seem to add up exactly,

EffPTS is almost

> always within 10 points of the actual total, usually

overestimating. Considering the

> shaky basis of my assumptions, I think that's pretty good --

although I'd like to get

> it closer. The one rule I gave myself: I'm not allowed to change

any of the weights,

> except for free throws. I still have no idea how much they are

worth with regards to

> possessions. Anybody have any ideas?

>

>

> ed ----- Original Message -----

From: <deano@...>

To: <APBR_analysis@yahoogroups.com>

Sent: Wednesday, February 05, 2003 10:29 AM

Subject: [APBR_analysis] Re: And while I'm at it...

> Ed --

>

> Take a look back at Message 14. That message discusses some of the

> other methods for weighting stats. JohnH of this group wrote a book

> with different weights. There is an economist named Dave Berri who

> also has something effectively similar. There are a few more on the

> web, too. I've developed a matrix showing the relative weights that

> the developers put on the different stats. I can't put that matrix

> out here since it's in the book I've got coming out.

>

Hmm, mostly 0.5 - 1.0, which is what I guessed.

> Yours is slightly different, of course, because you don't include any

> defensive stats, making it purely an offensive tool. That makes it

> somewhat unique.

>

I focus only on offense (and only part of the offense, for that matter) because I'm

incapable of developing an all-encompassing system. I prefer to let you guys slug out a

more comprehensive model -- I've seen how difficult it is. I'll focus on the small

stuff.

I think what makes it different than the others is it's theoretical basis. Most of the

methods you describe are linear weights-type systems, the

add-the-good-subtract-the-bad-to-arrive-at-a-rating models. Mine is a little different.

(First of all, I wanted it to look like a player's points total for a game, so you

would have an easy way of grasping what the rating means.) I assume those other ratings

used some kind of regression to arrive at weights that would produce results that jibe

with a qualitative assessment of player ability. I don't do that (I share your distaste

with linear weights). I only add and subtract stuff with regards to a teams expected

points per possession: Teams can expect 1 point per possession. If a player misses a

shot, he cost the team 1 point. If he turns the ball over, he cost the team 1 point.

Like I said, it's a pretty shaky basis on which to construct a rating system -- but it

seems to produce half decent results. I'd like it to be more accurate, but I can't seem

to do that without changing weights. I'm thinking that there may be a conceptual

problem with my approach that I'm overlooking. (Here's one: since missed shots usually

result in an offensive board 30% of the time, they can't possibly be worth -1 with

regards to a possession. But why does -1 give good results? I don't know.)- --- In APBR_analysis@yahoogroups.com, <igorkupfer@r...> wrote:

> Like I said, it's a pretty shaky basis on which to construct a

rating system -- but it

> seems to produce half decent results. I'd like it to be more

accurate, but I can't seem

> to do that without changing weights. I'm thinking that there may be

a conceptual

> problem with my approach that I'm overlooking. (Here's one: since

missed shots usually

> result in an offensive board 30% of the time, they can't possibly

be worth -1 with

> regards to a possession. But why does -1 give good results? I don't

know.)

Would -0.7 per missed FGA give better results? - --- In APBR_analysis@yahoogroups.com, "dlirag <dlirag@h...>" > a

conceptual> > problem with my approach that I'm overlooking. (Here's one: since

don't

> missed shots usually

> > result in an offensive board 30% of the time, they can't possibly

> be worth -1 with

> > regards to a possession. But why does -1 give good results? I

> know.)

There's not a lot of solid guidance on what the weights should be.

>

> Would -0.7 per missed FGA give better results?

If all you want are better results -- "better" is a personal

decision, so you can try it and see whether the results

are "better". Whether you also account for some teams rebounding

only 20% of their misses and other teams rebounding close to 40% is a

question. And if you modify the weight on missed FGA, should you

also modify the weight on offensive rebounds?

DeanO