From: ted.dunning@gmail.com   
      
   widowss wrote:   
   > using naive bayes classifier to calssify the public 20new groups.   
   > I filter the words whose letters are less than 3.   
   >  I stemmed the words.   
   > The left words are the elements of the feature vectors.   
   > when I chose 5 classes to be classified, the accuracy is about 45%.   
   > In the book "machine learning", it said that this accurancy can up to   
   > 89%.   
   > Can anybody tell me how to improve my classifier?Thanks a lot.   
   >   
      
   Which naive bayes classifier?  One you wrote?  If so, I would suspect a   
   programming bug.   
      
   What preprocessing are you doing to your text?   
      
   If you are using a well known program, then I would suspect that you   
   may be using a version that is not choosing term weights very well.   
   This will occur, for instance, when a word appears exactly once in the   
   training data.  Many systems will give this word a very high weight   
   which is unrealistic.   
      
   Also, in the quote from Machine Learning, was that accuracy on exactly   
   the same problem or on another one?  Problems differ in difficulty for   
   different approaches.   
      
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