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copied!<p>I am on Lucene core 3.0.3, but I expect the API will be very similar. This method will total up a term frequency map for a given set of Document numbers and a list of fields of interest, ignoring stop words.</p> <pre><code> /** * Sums the term frequency vector of each document into a single term frequency map * @param indexReader the index reader, the document numbers are specific to this reader * @param docNumbers document numbers to retrieve frequency vectors from * @param fieldNames field names to retrieve frequency vectors from * @param stopWords terms to ignore * @return a map of each term to its frequency * @throws IOException */ private Map<String,Integer> getTermFrequencyMap(IndexReader indexReader, List<Integer> docNumbers, String[] fieldNames, Set<String> stopWords) throws IOException { Map<String,Integer> totalTfv = new HashMap<String,Integer>(1024); for (Integer docNum : docNumbers) { for (String fieldName : fieldNames) { TermFreqVector tfv = indexReader.getTermFreqVector(docNum, fieldName); if (tfv == null) { // ignore empty fields continue; } String terms[] = tfv.getTerms(); int termCount = terms.length; int freqs[] = tfv.getTermFrequencies(); for (int t=0; t < termCount; t++) { String term = terms[t]; int freq = freqs[t]; // filter out single-letter words and stop words if (StringUtils.length(term) < 2 || stopWords.contains(term)) { continue; // stop } Integer totalFreq = totalTfv.get(term); totalFreq = (totalFreq == null) ? freq : freq + totalFreq; totalTfv.put(term, totalFreq); } } } return totalTfv; } </code></pre>

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