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InformationTheoryUtil.java
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InformationTheoryUtil.java
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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.metron.statistics.informationtheory;
import java.util.Map;
public enum InformationTheoryUtil {
INSTANCE;
private static final double LOG2 = Math.log(2);
public double entropy(Map<?, Integer> counts, double logOfBase) {
double ret = 0.0;
int n = 0;
if(counts == null || counts.isEmpty()) {
return ret;
}
for(Integer f : counts.values()) {
n+=f;
}
for(Integer f : counts.values()) {
double p = f.doubleValue()/n;
ret -= p * Math.log(p) / logOfBase;
}
return ret;
}
public double entropy(Map<?, Integer> counts, int base) {
return entropy(counts, Math.log(base));
}
public double bitEntropy(Map<?, Integer> counts) {
return entropy(counts, LOG2);
}
}