Naive Bayes classifier LongWritable exception

Question

I am trying to use the Naive Bayes classifier in Mahout to classify some products data.

I have used solr to convert both my datasets into lucene indexes, then used the Mahout split command to create the training and holdout sets. This appeared to work fine.

Now I am up to the stage of training the Naive Bayes model with trainnb, but I'm receiving the following error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
        at org.apache.mahout.classifier.naivebayes.BayesUtils.writeLabelIndex(BayesUtils.java:119)
        at org.apache.mahout.classifier.naivebayes.training.TrainNaiveBayesJob.createLabelIndex(TrainNaiveBayesJob.java:152)
        at org.apache.mahout.classifier.naivebayes.training.TrainNaiveBayesJob.run(TrainNaiveBayesJob.java:92)
        at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
        at org.apache.mahout.classifier.naivebayes.training.TrainNaiveBayesJob.main(TrainNaiveBayesJob.java:62)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:68)
        at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:139)
        at org.apache.mahout.driver.MahoutDriver.main(MahoutDriver.java:195)

This is my command input:

$MAHOUT_HOME/bin/./mahout trainnb -i ~/training_output/Amazon_training_output/ -el -o ~/model/Amazon -li ~/labelindex/Amazon -ow -c

What does the error mean in this context, and how do I resolve it?

Is it possible that my original index is to blame?

No, I ultimately rolled my own solution to the classification. I only used Mahout's n-grams libraries, and even that could have been done by another non-Mahout library. Sorry. — user2115543

nitin nitin · Accepted Answer · 2014-02-21T19:01:53

Maybe your key is not formatted correctly? Based on the code, I see the key is expecting /string/int

line 119, 131 http://grepcode.com/file/repository.cloudera.com/content/repositories/releases/org.apache.mahout/mahout-core/0.7-cdh4.1.3/org/apache/mahout/classifier/naivebayes/BayesUtils.java?av=f

Naive Bayes classifier LongWritable exception

1 Answers