/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.classifier.naivebayes;
/** Implementation of the Naive Bayes Classifier Algorithm */
public class StandardNaiveBayesClassifier extends AbstractNaiveBayesClassifier {
public StandardNaiveBayesClassifier(NaiveBayesModel model) {
super(model);
}
@Override
public double getScoreForLabelFeature(int label, int feature) {
NaiveBayesModel model = getModel();
// Standard Naive Bayes does not use weight normalization
return computeWeight(model.weight(label, feature), model.labelWeight(label), model.alphaI(), model.numFeatures());
}
public static double computeWeight(double featureLabelWeight, double labelWeight, double alphaI, double numFeatures) {
double numerator = featureLabelWeight + alphaI;
double denominator = labelWeight + alphaI * numFeatures;
return Math.log(numerator / denominator);
}
}