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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 2, 2013nership.  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;

public class LogLikelihood implements AssociationRate {

	private double getLogLike(double x) {
		return x * Math.log(x);
	}
	
	@Override
	public double getValue(int a,int b,int c,int d) {
		return 
			this.getLogLike(a) 
			+ (b <= 0 ? 0.0 : this.getLogLike(b))
			+ (c <= 0 ? 0.0 : this.getLogLike(c))
			+ this.getLogLike(d)
			+ this.getLogLike(a + b + c + d)
			- this.getLogLike(a + b)
			- this.getLogLike(a + c)
			- this.getLogLike(b + d)
			- this.getLogLike(c + d)
			;
	}
	
}