Nave Bayes Classifier and probability calculation for a single test example

[skasab2s <sk...@smail.inf.fh-brs.de>]

Hello,

I tried out Mahout's Naive Bayes example for "history and science" and it
worked great! I have a question about the classifying part:

  for (Map.Entry<String, List<String>> stringListEntry :
document.entrySet()) {
              List<String> strings = stringListEntry.getValue();
              ClassifierResult classifiedLabel = classifier.classify(model,
                  strings.toArray(new String[strings.size()]),
                  defaultCat);
  ...
boolean correct = resultAnalyzer.addInstance(correctLabel, classifiedLabel);
}

As a result for a single test example (in this case 'document'), we get a
boolean value. I'm a little bit confused, because as far as I know, Naive
Bayes is a probabilistic model
(http://en.wikipedia.org/wiki/Naive_Bayes_classifier) and when classifying a
single instance, it should return a probability (measured in percentage, and
not in true/false). 

So, how can I get a percentage instead of a boolean when using Naive Bayes /
Complementary Bayes?

Many thanks and best regards!

Svetlomir Kasabov   

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Re: Nave Bayes Classifier and probability calculation for a singletest edxample

[ta...@gmail.com]

Sent from BlackBerry® on Airtel

-----Original Message-----
From: gaurav garg <ga...@gmail.com>
Date: Wed, 4 May 2011 00:37:53 
To: <us...@mahout.apache.org>
Reply-To: user@mahout.apache.org
Cc: <ma...@lucene.apache.org>
Subject: Re: Nave Bayes Classifier and probability calculation for a single
 test example

Hi Svetlomir,

You can use ClassifierContext class (
https://builds.apache.org/hudson/job/Mahout-Quality/javadoc/index.html?org/apache/mahout/common/StringTuple.html)
to get the top N matching result and their respective scores.

Hope it helps.

Thanks
Gaurav

Re: Nave Bayes Classifier and probability calculation for a single test example

[gaurav garg <ga...@gmail.com>]

Hi Svetlomir,

You can use ClassifierContext class (
https://builds.apache.org/hudson/job/Mahout-Quality/javadoc/index.html?org/apache/mahout/common/StringTuple.html)
to get the top N matching result and their respective scores.

Hope it helps.

Thanks
Gaurav