/*******************************************************************************
* Copyright 2015-2016 - CNRS (Centre National de Recherche Scientifique)
*
* 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.
*
*******************************************************************************/
/*
* 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 2, 2015nership. 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 eu.project.ttc.metrics;
import eu.project.ttc.models.ContextVector;
import eu.project.ttc.models.Term;
public class Cosine extends AbstractSimilarityDistance {
@Override
protected double getValue(ContextVector source, ContextVector target, Explanation expl) {
double sourceSum = getSquareSum(source);
if(sourceSum == 0d)
return 0d;
double targetSum = getSquareSum(target);
if(targetSum == 0d)
return 0d;
double sum = 0d;
for (Term t : source.terms()) {
double partial = source.getAssocRate(t) * target.getAssocRate(t);
if(partial > 0)
expl.addExplanation(t, partial);
sum += partial;
}
return sum / Math.sqrt(sourceSum * targetSum);
}
private double getSquareSum(ContextVector vec) {
double sum = 0.0;
double val;
for (Term t : vec.terms()) {
val = vec.getAssocRate(t);
sum += val * val;
}
return sum;
}
}