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 ( 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.