org.apache.tika.eval.textstats.CommonTokensKLDNormed Maven / Gradle / Ivy
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package org.apache.tika.eval.textstats;
import java.util.List;
import java.util.Map;
import org.apache.commons.lang3.mutable.MutableInt;
import org.apache.commons.lang3.tuple.Pair;
import org.apache.commons.math3.util.FastMath;
import org.apache.tika.eval.langid.Language;
import org.apache.tika.eval.tokens.CommonTokenCountManager;
import org.apache.tika.eval.tokens.LangModel;
import org.apache.tika.eval.tokens.TokenCounts;
public class CommonTokensKLDNormed implements LanguageAwareTokenCountStats {
private final CommonTokenCountManager commonTokenCountManager;
public CommonTokensKLDNormed(CommonTokenCountManager mgr) {
this.commonTokenCountManager = mgr;
}
@Override
public Double calculate(List languages, TokenCounts tokenCounts) {
Pair pair = commonTokenCountManager.getLangTokens(languages.get(0).getLanguage());
LangModel model = pair.getValue();
double kl = 0.0;
if (tokenCounts.getTokens().entrySet().size() == 0) {
return 1.0;
}
double worstCase = 0.0;
for (Map.Entry e : tokenCounts.getTokens().entrySet()) {
double p = (double)e.getValue().intValue()/(double)tokenCounts.getTotalTokens();
if (p == 0.0) {//shouldn't happen, but be defensive
continue;
}
double q = model.getProbability(e.getKey());
kl += p * FastMath.log(q / p);
}
for (int i = 0; i < tokenCounts.getTotalTokens(); i++) {
double worstCaseP = 1/(double)tokenCounts.getTotalTokens();
worstCase += worstCaseP * FastMath.log(model.getUnseenProbability()/worstCaseP);
}
return (kl/worstCase);
}
}