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March 29, 2008

Rebounding by Shot Location

Posted by Eli in Raw Stats

Here’s a chart of offensive rebounding percentage by shot location, as suggested by Eric in the comments to my last post. The chart doesn’t show where players grab rebounds on the court (I don’t have that data), instead it shows which shot locations result in more offensive rebounds.

This took a little more work to construct because rebounds are listed in separate lines of the play-by-play than shot attempts (and not always on the very next line), and because the league credits a rebound for all missed shots, even half-court heaves at the end of a quarter where the clock expires while the ball is in the air. I tried to eliminate as many of these bookkeeping rebounds from the data as I could (though the red squares on the longest threes suggest that some still remain, as the offensive team is typically credited with the bookkeeping rebound).

I smoothed out the data as I did on the FG% chart, so each 1×1 ft square actually represents the offensive rebounding percentage on shots taken from the surrounding three-foot by three-foot square on the court. The color scale runs from blue (low ORB%) to yellow (average ORB%) to red (high ORB%). The data is from the 03-04 to 06-07 seasons.

Which Shots are Offensive Rebounded - ORB% by Shot Location:

The conventional wisdom on this topic that one usually hears from broadcasters is that it’s easier to get offensive rebounds on three-pointers because of the long caroms. However, Dean Oliver, John Hollinger and others have done research suggesting that there is actually a higher offensive rebounding percentage on twos than threes (see this thread and this study).

This chart suggests that both sides are onto something - longer three-point jumpers are rebounded by the offense more often than shorter two-point jumpers, but shots in the paint are rebounded by the offense even more frequently than three-pointers. Interestingly, it also looks like jumpers from the right baseline are offensive rebounded more frequently than jumpers from the left baseline, but I’d have to take a closer look at the data to confirm that.

March 27, 2008

More Shot Charts

Posted by Eli in Raw Stats

Here are a few more shot charts along the lines of those from my previous post.

First, a chart of effective field-goal percentage by shot location, which some commenters requested. eFG% is basically a measure of points per shot (excluding points from free throws) that is different from FG% in that it gives extra credit for made threes. The formula is 0.5*(2*2PM + 3*3PM)/(2PA + 3PA). I didn’t smooth out the data like I did in the FG% chart, so each one-foot by one-foot square contains the eFG% on shots from that spot. The color scale runs from blue (low eFG%) to yellow (average eFG%) to red (high eFG%).

Where Players Score Points - eFG% by Location:

As expected, three point shots get a big boost by looking at eFG% rather than just FG%. Shots right around the basket (dunks and layups mainly) also rate well, as do elbow jumpers, anything down the center line of the court, and small areas on the left and right blocks. The red squares just inside the three-point line are artifacts of three-point makes that were mistakenly coded as being taken from inside the three-point line.

The other new chart shows in which locations shots are most likely to get blocked. Each one-foot by one-foot square represents the percent of field goal attempts from that spot that were blocked. The color scale runs from blue (few blocks/FGA) to yellow (some blocks/FGA) to red (many blocks/FGA). The results are basically as expected - most blocks occur close to the hoop.

Where Shots Get Blocked - Blocks/FGA by Location:

If anyone has any other suggestions let me know.

Where Players Take and Make Shots

Posted by Eli in Raw Stats

I haven’t posted in a while, but I have a good excuse. I’ve been assembling a database of play-by-plays from the last five seasons. This will make it much easier to investigate many areas of the game. It’s not completely finished yet, but already there’s a lot of interesting stuff that I can pull from the database. For example, I can quickly calculate that in the four seasons from 2003-04 to 2006-07 (I’m missing a few games, but I have over 99% of games from that time period), there were 14,216 hook shots taken. 45.5% of those shots were made, 54% of those makes were assisted, and 4% of all hook shots were blocked. But that’s not what I really want to examine in this post. Instead I’m going to look at shot location data.

During all NBA games, diligent game charters sit courtside and mark the location of every shot taken on the court down to the square foot. I believe this is done by using a stylus on a touchscreen monitor with a replica of the court on it. This is the source of the shot charts you can see after a game on ESPN.com or CBS Sportsline, and of the compiled shot charts of NBA.com’s Hot Spots (which I discussed in my first post). With the play-by-play database I’ve constructed it’s possible to look at this shot location data in a number of ways.

First, below is a picture showing where players shoot from. Again it’s based on data from 03-04 to 06-07. The court dimensions are to scale, and each one-foot by one-foot square on the court is color-coded based on the number of field goal attempts from that spot. The color scale runs from blue (few FGA) to yellow (some FGA) to red (many FGA). Obviously the charted locations aren’t 100% accurate, but there are still some very interesting patterns that emerge.

Where Players Take Shots - FGA by Location:

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January 18, 2008

Pretty Pictures from Google Spreadsheets

Posted by Eli in Raw Stats, Site Tips

Alex from the blog Mistake by the Lake recently had a post that utilized some of the tips I posted for scraping HotSpots/HotZones data in combination with some neat Google Spreadsheets features to display some charts about Larry Hughes that automatically update throughout the season. I thought this was a great idea, and I didn’t know it was even possible. In this post I’m going to create some charts of my own and explain how anyone can use these very cool features from Google Spreadsheets.

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December 6, 2007

More stats on the way?

Posted by Eli in Raw Stats

SI.com has an article up on new basketball stats which includes some interesting quotes from Gregg Popovich on how he views stats. This part of the article caught my eye:

The good news is that, just like media options, stats are changing. A sterling example: At NBA.com, box scores for the 2007-08 season now include plus/minus ratings for each player and a category labeled “BA” for blocks against. Even better news is that deflections and contested shots are being studied this season to see how trackable and reliable they would be, as two more stats worth adding.

It’s great that the league is making advancements in their statistical tracking. A lot of teams have been keeping track of stats like deflections for years, but that stays behind closed doors. When the league gets involved then the public can have access to the data and run with it, as has happened with MLB’s Enhanced Gameday and PITCHf/x data. And any additional defensive statistics would definitely be useful considering the current lack of stats on that side of the ball.

November 13, 2007

Some HotZones data to work with

Posted by Eli in Raw Stats

OK, here’s some of the HotZones data I promised. I’ve uploaded the team by team data to Swivel - offensive data from 03-04 to 06-07, and defensive data from 03-04 to 06-07. You should be able to download each as a .CSV file and easily import them into a spreadsheet or database.

I’ll have more analysis later, but for now here’s a quick look at how frequently and how well teams shot from different distances.

League percent of FGA taken from each distance:

         0-8 ft  8-16 ft  16-24 ft  24+ ft
         ------  -------  --------  ------
2003-04   40.6%    18.0%     22.9%   18.5%
2004-05   40.5%    16.4%     23.7%   19.4%
2005-06   41.1%    15.2%     23.7%   20.0%
2006-07   41.3%    14.7%     23.0%   21.0%
-------  ------  -------  --------  ------
  Total   40.9%    16.1%     23.3%   19.7%

League field-goal percentage by distance:

         0-8 ft  8-16 ft  16-24 ft  24+ ft
         ------  -------  --------  ------
2003-04   53.7%    37.7%     38.8%   35.1%
2004-05   54.6%    38.3%     40.0%   36.0%
2005-06   55.3%    39.0%     40.5%   36.2%
2006-07   56.3%    39.6%     40.4%   36.2%
-------  ------  -------  --------  ------
  Total   55.0%    38.6%     39.9%   35.9%

The potential trends that pop out to me are the decline in shots being taken from 8-16 feet and the increase in shots from 0-8 feet and 24+ feet. As far as FG% by distance goes, teams seem to be shooting better from both 0-8 feet and 8-16 feet.

You can see that a lot of shots are taken from 0-8 feet. This is where 82games’ distance breakdowns are useful, as their categories of dunks, tips, and close shots provide divisions within 8 feet (some of the shots they classify as jumpers are also within 8 feet).

Another thing to note is that 24+ feet FG% differs slightly from three-point percentage because the HotZones data excludes shots from beyond half-court.

For reference, here are league-wide boxscore stats by season from Basketball-Reference.

November 11, 2007

So much for HotZones

Posted by Eli in Raw Stats, Site Tips

Well, wouldn’t you know it, right after I published my long piece on NBA.com’s HotZones, they decided to change them. The HotZones page is still functional and linked to from NBA.com, but the latest incarnation is now called NBA Hot Spots. It doesn’t appear to have any new features, but the menus do allow you to access more of the data that the HotZones page didn’t (the 07-08 regular season and preseason, and the 06-07 playoffs). It looks like it’s just a new front-end, so all the tips from my previous post should still work, as the data is still stored in the same place on the NBA.com server. Hat tip to Hoopinion for noticing the move.

November 8, 2007

Hacking HotZones

Posted by Eli in Raw Stats, Site Tips

The folks at the official NBA site added a great feature a few years back called HotZones. It’s not on the level of MLB.com’s fantastic PITCHf/x data, but it’s useful nonetheless. It consists of season-level shot charts for every player and team, broken down into 14 zones. This is data that wasn’t previously available. ESPN has had game-by-game shot charts with their boxscores since 02-03, but in a basically unusable form. 82games has shooting by distance since 02-03, but in addition to lacking side-to-side splits it groups shots into pretty large distance categories (what they label “Jump” shots includes some shots closer than 8 feet as well as everything beyond 8 feet).

So NBA.com’s HotZones offer a lot of valuable information, but unfortunately they are also presented in a very difficult to use format. They are embedded in a Flash application, which means easy linking as well as copying and pasting are out of the question. Though you can select any team or player and a variety of splits, there’s no way to see what the league average FG% is for a specific zone, or who the league leaders are. And because of errors in the Flash menus, you can’t even access a lot of the available data (as of this posting, data is present on the server but inaccessible through the Flash menus for players from past seasons who are no longer in the league, the 07-08 regular season, the 06-07 playoffs, and the 03-04 regular season). However, with a bit of digging, I was able to find some ways around these problems. What follows are instructions for how to link to HotZones pages (including those you can’t get to through the menus) and how to download HotZones data in a format that allows for easy manipulation in a spreadsheet.

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