The Bayes example package provides some helper classes for training the Naive Bayes classifier on the Twenty Newsgroups data. See {@link org.apache.mahout.classifier.bayes.PrepareTwentyNewsgroups} for details on running the trainer. See {@link org.apache.mahout.classifier.bayes.PrepareTwentyNewsgroups} for details on formatting the Twenty Newsgroups data properly for the training.
The easiest way to prepare the data is to use the ant task in core/build.xml:

        ant extract-20news-18828

This runs the arg line:

        -p ${working.dir}/20news-18828/ -o ${working.dir}/20news-18828-collapse -a ${analyzer} -c UTF-8

To Run the Wikipedia examples (assumes you've built the Mahout Job jar):

1. Download the Wikipedia Dataset. Use the Ant target: ant enwiki-files
2. Chunk the data using the WikipediaXmlSplitter (from the Hadoop home):
   bin/hadoop jar <PATH TO MAHOUT>/target/mahout-examples-0.2 org.apache.mahout.classifier.bayes.WikipediaXmlSplitter -d <MAHOUT_HOME>/examples/temp/enwiki-latest-pages-articles.xml -o <MAHOUT_HOME>/examples/work/wikipedia/chunks/ -c 64

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