Everyone Else Is Robots

Collapsing v. Deleting

2011-02-15T16:48:00.000-08:00

I am in the midst of implementing my own CART decision tree and ran into a semantic snag. In Hastie's book, The Elements of Statistical Learning, it is stated that the best way to determine the size of the decision tree is to grow a large tree and then prune it afterwards.

In this process, internal nodes are "collapsed". It wasn't until I started implementing this that I realized I was not clear on what was meant by collapsing. Initially I thought it meant deleting a node from the tree, which is wrong.

I had to grab Brieman's original book, Classification and Regression Trees to find out what was meant, and feel a little foolish now knowing how simple the answer is. Collapsing a node simply means removing the entire subtree below, but not including, that node. -_____-

The book includes a nice diagram which I figure would be helpful for anyone whoever reads this. Basically the following is a demonstration of collapsing the tree at node T2, i.e., T-T2.

Words of WIsdom

2010-11-24T10:46:00.000-08:00

I am nearing the end of my machine learning coarse and felt it was time to share different quotes my professor has said throughout the quarter. They are both deep and provacative:

1. [Said very dramatically] "You can't get around the noise!"

2. "There are worse things than gradient descent to take on faith."

3. "Son, you need to avoid gradient descent algorithms."

4. "There is a good chance today's lecture won't come out well."

5. "They're sexy because they have the word neural in them."

6. "Why do math classes take so long?"

7. "And how do you do that? Don't worry. It's just math, you don't have to implement it."

8. "It doesn't really exist but that isn't going to stop us from writing it down."

9. "It's about exactly approximate to it, not approximately approximate to it."

10. "Now I want to show you a picture. Why? Because I like this picture. It makes me happy."

Android - Live Wallpapers

2010-11-19T14:21:00.000-08:00

I have decided to waste my time noodling with developing a live wallpaper for Android. Here's where I am at.

1. ADK downloaded and working. This process can really only be described as delightful. I cannot believe how easy it was.

2. Get the samples. The ADK comes with a number of examples that can be downloaded through eclipse. Window -> Android SDK and AVD Manager -> Available Packages -> Download all that noize. Everything that gets downloaded into wherever you unzipped the ADK tarball. In that directory there should now be a samples directory filled with all kinds of goodies.

3. Run sample live wallpaper. File -> New -> Project -> Android -> Android Project -> Next. Select the "Create project from existing source" radio button. Browse -> /samples/android-8/CubeLiveWallpaper. Finish.

4. Right click the project that appears -> Run as -> Android Application.

5. Under Live Wallpapers on the emulator, the cube examples will now be available.

6. Collect the cash.

Making my own wallpaper is now as easy as modifying the template that has been provided. The next step is to figure out what the heck I want the wallpaper to do.

Jai in eclipse

2009-12-18T00:54:00.000-08:00

I find java's website an atrocity. Here is my approach to get JAI working with eclipse.

1. Download the platform independent JAI, jai-1_1_3-lib.zip, by going here, and clicking on the binary builds link under Downloads.

2. Open the .zip that was downloaded, open the folder called lib within, and extract both the .jar files(jai_codec and jai_core) there to any convenient location.

3. Within eclipse right click the java project which needs to use the JAI library and click properties.

4. Click on the build path option and select the Libraries tab.

5. Click the Add External Jars... button.

6. Select jai_codec.jar and press OK. Click the Add External Jars... button again, select jai_core.jar and press OK.

7. JAI is now accessible from within the project but there will be no included documentation. To get the API documentation, begin by downloading the .zip containing said documentation here.

8. Under the java project, click the Referenced Libraries pull down.

9. Right click jai_core.jar and select Properties.

10. Click the Javadoc Location option.

11. Click the Javadoc in archive option.

12. Under Archive path click Browse... Find and select the .zip that was downloaded and press OK.

13. Repeat steps 9-12 replacing jai_core.jar with jai_codec.jar and using the same javadoc .zip file.

14. Finished

Libtiff in eclipse

2009-12-11T15:19:00.000-08:00

I recently started on a project that involves reading form .tiff files. The first step is to get the libtiff API up and running. This package contains several functions that handle simple operations, such as opening and reading data from a .tiff file.

1. I am using Ubuntu so downloading the libtiff library is as simple as:
sudo apt-get install libtiff4-dev
2. This will put the library in /usr/local. The eclipse editor is smart enough to look at this directory so you can call auto-complete on functions from the library but when it comes time to compile, any function calls will not be recognized by the G++ compiler. We need to include the library for the linker.

3. Go to project->properties-> .

4. In the window that opens up, open up the C/C++ Build option.

5. Click the Settings option that pops down.

6. Under the Tool Settings tab open up the GCC C++ Linker option.

7. Click on the Libraries option.

8. Under the Libraries (-l) pane that opened click the add icon (page with a + sign on it).

9. Type in tiff and click OK.

10. Click OK of the properties window.

11. We can now build without any unrecognized TIFF functions.

Weka in Eclipse

2009-09-22T11:49:00.000-07:00

I succeeded in opening Weka source as a project in Eclipse today, and I found a much easier way to do so than the method posted on Weka's homepage.

1. Get Weka from the internets here . Extract the contents to a destination of your choosing.

2. In the extracted folder extract the contents weka-src.jar to yet another destination of your choosing.

2. Open Eclipse

3. File -> New -> Project...

4. Select Java Project from an Existing Ant Buildfile. Hit Next.

5. Hit the Browse... button next to the Ant Buildfile: text box. Locate the folder to which you extracted the files in weka-src.jar. Select the build.xml file that is there.

7. Click finish

Eclipse breakpoint conditions

2009-07-16T11:38:00.000-07:00

Today was the first time I needed to set multiple conditions on a single break point.

To start, double click the line at which you wish to have the break point set. Then right click the resulting blue dot and select Breakpoint Properties... Click the box for Enable Condition, and then fill in the desired condition.

To set a single condition is easy. Given you want to stop the program at the line when the user number is 8:

user == 8

No semicolon or anything required. To do more than that you treat the condition as one big boolean expression. Lets say I wanted the user number to be 8 but I also wanted the exercise number to be 3:

user == 8 && exercise == 3

It is just like filling in the insides of an if statement.