Archive for July, 2011

July 7, 2011

Best loss function for gradient boosting?

I know that is an ill-defined question. But it would be assuring to know that a loss function does not perform worse than you expected.

Here is a small experiment with the staple data set for classification: the spam data.

  • 2/3 of the data is used for training and the remaining 1/3 for testing.
  • The gbm package is used with tree-depth=2 and the default settings for other parameters.
  • Two loss functions: “Bernoulli” and “Adaboost”
The results: 4.1% testing error rate for “Bernoulli” and 5.5% testing error rate for “Adaboost”. According to the ElemStatLearn book, logistic regression has around 5.5% testing error rate; does the experiment show that “Adaboost” loss function is no better than vanilla logistic regression?
July 6, 2011

Windows XEmacs “List and Install” Problem

After I installed Windows 7, the package manager in XEmacs stopped working. In particular, the “List and Install” function did not work with the main ftp site (ftp.xemacs.org). The connection to the ftp server could be established, but the packages couldn’t be listed.

Here is the fix that worked on my computer.

1. Customize “efs-ftp-program-name”
2. Change the value from “C:/Windows/SysWOW64/ftp.exe” to the standard setting, which is just “ftp”. And Voila!

I don’t know how it worked. If you know, let me know.