org.apache.tika.eval.textstats.TokenEntropy Maven / Gradle / Ivy
/*
* 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.tika.eval.textstats;
import org.apache.commons.lang3.mutable.MutableInt;
import org.apache.commons.math3.util.FastMath;
import org.apache.tika.eval.tokens.TokenCounts;
public class TokenEntropy implements TokenCountStatsCalculator {
@Override
public Double calculate(TokenCounts tokenCounts) {
double ent = 0.0d;
double p = 0.0d;
double base = 2.0;
double totalTokens = (double)tokenCounts.getTotalTokens();
for (MutableInt i : tokenCounts.getTokens().values()) {
int termFreq = i.intValue();
p = (double) termFreq / totalTokens;
ent += p * FastMath.log(base, p);
}
return -1.0*ent;
}
}