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Assisted % - Creating Your Own Shot?
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Ben F.



Joined: 07 Mar 2005
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PostPosted: Sun Mar 13, 2005 10:28 am    Post subject: Assisted % - Creating Your Own Shot? Reply with quote

As brought up in the "How well would this team perform?" thread, I wonder about the validity of using assisted%, at least in small part, to find out how well someone can create their own relatively high percentage shot.

I think this would be something very interesting to look at, but really don't have a clue how to measure it. I don't think it should be done on a league-wide basis, but rather, on a player by player basis. I think there's something here, but I just can't quite put my finger on it. Hopefully you guys can help me out.

Let's take a look at Kobe Bryant, for example.

Year - Assisted% - FG% - eFG%

0203 - 40% - 45.1% - 48.2%
0304 - 47% - 44.1% - 47.1%
0405 - 30% - 42.6% - 46.7%

Personally, I think this can tell you something about Kobe. It seems that his eFG% has only taken a slight dip with the huge drop off in assisted%.

Now let's look at Dirk.

0203 - 66% - 46.3% - 51.4%
0304 - 72% - 46.2% - 50.0%
0405 - 53% - 45.2% - 48.4%

Dirk also had a huge drop off in assisted% this last year. In fact, his pattern followed about the same pattern as Kobe's over the last 3 years - bump up in asst'd%, then huge drop off, with a steadying decline in efficiency. Both are regarded as stars and have still been able to maintain a fairly efficient presence while creating more for themselves.

But now let's look at Richard Jefferson, who is clearly not on the same level as these two.

0203 - 68% - 50.1% - 50.4%
0304 - 70% - 49.8% - 52.1%
0405 - 54% - 42.2% - 44.9%

All these three players' assisted percentages dropped off by at least 15%. However, with the first two superstars, eFG% dropped by at most 1.6%. With Jefferson? 7.2%.

What I'm trying to say is that I think there's something there. I think you can come up with something similar to Dean's efficiency curves, player by player. Instead of usage, look at how often they are assisted.

I know there are problems with what I've presented above - different factors you could look at as to what the difference is between those players. But I still think that something can be taken out of this.
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gabefarkas



Joined: 31 Dec 2004
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PostPosted: Mon Mar 14, 2005 11:31 am    Post subject: Reply with quote

this is something i'm very interested in investigating further, but i'm not sure if there's enough data out there to accurately look at it.

specifically, i would love to be able to come up with a chart for each player that shows efficiency vs assisted% (with assisted% as the independent variable)....i guess this would be similar to Ch 19 of DeanO's book.
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Ben F.



Joined: 07 Mar 2005
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PostPosted: Tue Mar 15, 2005 4:38 pm    Post subject: Reply with quote

I'm looking at cutting up the play-by-plays and analyzing this on a game-by-game basis. Graphing Assisted% vs. 2pt-FG% and Assisted% vs. 3ptFG% per game, and trying to get a "skill curve" type readout from that.

2 things:
a) Do you think this would be worthwhile? Ways to improve this study?
b) Does anyone have an already written out list of the NBA schedule (in excel of some kind of format that I can cut up) so that I can easily get a list of links to the play-by-play?

Thanks for the help.
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HoopStudies



Joined: 30 Dec 2004
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PostPosted: Tue Mar 15, 2005 4:54 pm    Post subject: Reply with quote

FFSBasketball wrote:
"Insanity: doing the same thing over and over again and expecting different results." -Albert Einstein


Hmm, isn't that what basketball teams do 82 times a year? Wink
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Ed Küpfer



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PostPosted: Tue Mar 15, 2005 5:31 pm    Post subject: Reply with quote

FFSBasketball wrote:
Does anyone have an already written out list of the NBA schedule (in excel of some kind of format that I can cut up) so that I can easily get a list of links to the play-by-play?


For this season, no, but it's not difficult for me to put together. If, however, you'd want to use previous seasons, I have those ready to go. I even have the actual logs in HTML and ascii, although the latter is messy. Tell me exactly what you want. NBA.com, ESPN, Sportsline?
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Ben F.



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PostPosted: Tue Mar 15, 2005 6:14 pm    Post subject: Reply with quote

Well, I can fairly easily write a parser to pick apart the play-by-play logs and find what I want - the difficulties lie in directing the parser to the right place.

I know that at least this year, the play-by-play on the NBA website is at the address of the following formula:

http://scores.nba.com/games/yyyymmdd/AwayTeamHomeTeam/PlayByPlayPrint.html

So the hard part that I was looking for help on was getting the schedule, so that I could have a list of games with their date to direct the parser to.

If you have the actual play-by-play logs from previous years, that would be great. Once again though, the schedule would be necessary (unless you have the files in a numbered order, or something) so that the parser would know the file name to go to.

If you can help with any of this, that would be great.

P.S. I would prefer the NBA logs, if you could e-mail them to FFSBasketball ]at[ gmail ]dot[ com. Thanks a bunch.
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Ben F.



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PostPosted: Tue Mar 15, 2005 7:16 pm    Post subject: Reply with quote

Also, before embarking on this study, are there any suggestions of a better way to do it, or something to look into while doing it?
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Ed Küpfer



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PostPosted: Tue Mar 15, 2005 7:32 pm    Post subject: Reply with quote

FFSBasketball wrote:
Also, before embarking on this study, are there any suggestions of a better way to do it, or something to look into while doing it?


Variables to keep track of:

* Assister
* Assistee
* Type of shot (layup, dunk, 3pt, etc.)
* Maybe the score and time at the attempt

I don't think you really need much more than that. Once you have these, there are all kinds of cool things you can do. I am particularly interested in applying DanR's Potential Assists calculations. Player-player hookups would be the sexy study, but I'm not so sure how informative it would be due to small samples. Using type of shot as a proxy for area on the floor, you'll be able to tell where players tend to get assisted, and where they make their own shots. I'm sure others can come up with better ideas than mine.
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Ben F.



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PostPosted: Tue Mar 15, 2005 8:18 pm    Post subject: Reply with quote

OK, well this is a slightly different approach to what I was thinking, but it might make more sense, because it's more general, which means there's more data possible.

The only problem with what you presented is how to record the data. Should it just be in a list, delimited by commas or something?

So a sample would be:
Time,Score,Assistee,type of shot,assister
3:40,33-40,Odom,Running Jump,Atkins

How exactly would this help? It would seem we're back with the same problem as in the play-by-plays. That information is right in the play-by-plays, the key is how to categorize it.

What I was going to do was for each player have a column in the database for assisted%, and one for FG%. Delimit each game in those columns by commas, then be able to paste it into excel and make a graph for anyone you want of their assisted% vs. FG%.

The parser could always be run again for 2ptFG%, 3ptFG%, eFG%, or whatever measure you wish.
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Ed Küpfer



Joined: 30 Dec 2004
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PostPosted: Tue Mar 15, 2005 8:28 pm    Post subject: Reply with quote

FFSBasketball wrote:
So a sample would be:
Time,Score,Assistee,type of shot,assister
3:40,33-40,Odom,Running Jump,Atkins


How about:
Code:

Quarter   Time   Score   Assistee    TypeOfShot   Assister
1         3:40   -7      Odom       Running Jump   Atkins

Score would be presented as the difference between the scoring team and the opposing team. Comma delim is fine.

FFSBasketball wrote:
What I was going to do was for each player have a column in the database for assisted%, and one for FG%. Delimit each game in those columns by commas, then be able to paste it into excel and make a graph for anyone you want of their assisted% vs. FG%.


Excel only allows 255 columns, so you won't be able to put many games together on one sheet. Hmm....
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Ben F.



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PostPosted: Tue Mar 15, 2005 8:37 pm    Post subject: Reply with quote

There are many ways to get around excel, so that's not that big of a deal (for example, just rotate the table so columns become rows, and you can have unlimited rows - you can do this with Paste Special -> Transpose).

I think I'll do my original study first, see how it turns out, and then I'll edit the parser to take data that anyone else requests. That shouldn't be too hard. I'll let you know when I have results.
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gabefarkas



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PostPosted: Tue Mar 15, 2005 9:38 pm    Post subject: Reply with quote

i had envisioned the same thing, where it's sort of like the skill curves. put assisted% on the x-axis, and efg% on the y-axis.
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Ben F.



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PostPosted: Tue Mar 15, 2005 11:29 pm    Post subject: Reply with quote

First off, thanks to Ed for the help.

Well, I got the parser working, and cut up the Hawks' PBPs from last year.

I'll post Terry's and Stephen Jackson's (added Reef, Sura and Ratliff) "skill curves" (we'll have to come up with another name), and you can take from them what you want.

The x-axis is assisted%, and the y-axis is FG% (straight, not eFG%).

Just a disclaimer: I compared my totals, and they look a little off of the actual NBA totals, so I'll investigate what the problem is later. For now though, they're pretty accurate.

Stephen Jackson


Jason Terry


Added in Shareef's 53 games with ATL:


More - Sura:


And Ratliff:


Obviously this is only 5 players, so it's hard to judge, but it seems to me you can take some general patterns from them.

All of the first three are relatively stable, and can create their own fairly good looks (I think this was somewhat expected with this caliber of player). But Reef and Jackson trend up slightly, suggesting they are still better set up by a passer, while Terry, as a PG, seems more comfortable creating his own shot, as he has a slight (very slight) downward trend.

Note: Terry's year-by-year data supports this finding - he's more efficient creating for himself. The last two years his ast'd% has been around 45%, and his FG% around 42%. This year, his ast'd% has gone down to about 35%, while his FG% has risen to over 50%.

As for the last 2, Sura is hard to judge, because of a fairly small sample size, and he's all over the place.

Ratliff is, as expected, trending upwards. His best looks are not set up by his moves, but by the passer.
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S.K.



Joined: 18 Feb 2005
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PostPosted: Wed Mar 16, 2005 2:37 pm    Post subject: Reply with quote

Interesting stuff, FFS.

Are you making any allowances for offensive putbacks/tips? I would think that this would significantly affect the results for a guy like Ratliff - it would technically count as "creating" the shot, but reflects rebounding skill rather than shot creation ability.
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S.K.



Joined: 18 Feb 2005
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PostPosted: Wed Mar 16, 2005 2:43 pm    Post subject: Reply with quote

Wait, that didn't make sense - you're trying to use assisted% only as an indicator. I should think things through before I post.

Well, anyway, I think it would be worthwhile to try subtracting 'tips' from the unassisted FG, since they'll never be assisted.
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