public Explanation idfExplain(CollectionStatistics collectionStats, TermStatistics termStats) {final long df = termStats.docFreq();final long docCount = collectionStats.docCount();final float idf = idf(df, docCount);return Explanation.match(idf, "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5)) from:",Explanation.match(df, "n, number of documents containing term"),Explanation.match(docCount, "N, total number of documents with field"));}

public virtual Explanation IdfExplain(CollectionStatistics collectionStats, TermStatistics termStats){long df = termStats.DocFreq;long max = collectionStats.MaxDoc;float idf = Idf(df, max);return new Explanation(idf, "idf(docFreq=" + df + ", maxDocs=" + max + ")");}
