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/**
* 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;
import org.apache.mahout.classifier.AbstractVectorClassifier;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.Vector.Element;
/**
* Class implementing the Naive Bayes Classifier Algorithm. Note that this class
* supports {@link #classifyFull}, but not {@code classify} or
* {@code classifyScalar}. The reason that these two methods are not
* supported is because the scores computed by a NaiveBayesClassifier do not
* represent probabilities.
*/
public abstract class AbstractNaiveBayesClassifier extends AbstractVectorClassifier {
private final NaiveBayesModel model;
protected AbstractNaiveBayesClassifier(NaiveBayesModel model) {
this.model = model;
}
protected NaiveBayesModel getModel() {
return model;
}
protected abstract double getScoreForLabelFeature(int label, int feature);
protected double getScoreForLabelInstance(int label, Vector instance) {
double result = 0.0;
for (Element e : instance.nonZeroes()) {
result += e.get() * getScoreForLabelFeature(label, e.index());
}
return result;
}
@Override
public int numCategories() {
return model.numLabels();
}
@Override
public Vector classifyFull(Vector instance) {
return classifyFull(model.createScoringVector(), instance);
}
@Override
public Vector classifyFull(Vector r, Vector instance) {
for (int label = 0; label < model.numLabels(); label++) {
r.setQuick(label, getScoreForLabelInstance(label, instance));
}
return r;
}
/** Unsupported method. This implementation simply throws an {@link UnsupportedOperationException}. */
@Override
public double classifyScalar(Vector instance) {
throw new UnsupportedOperationException("Not supported in Naive Bayes");
}
/** Unsupported method. This implementation simply throws an {@link UnsupportedOperationException}. */
@Override
public Vector classify(Vector instance) {
throw new UnsupportedOperationException("probabilites not supported in Naive Bayes");
}
}
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