Java tutorial
/** * 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.mahout.utils.vectors.io; import com.google.common.collect.Lists; import org.apache.commons.lang.StringUtils; import org.apache.mahout.clustering.Cluster; import org.apache.mahout.clustering.WeightedVectorWritable; import org.apache.mahout.common.Pair; import org.apache.mahout.math.Vector; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.IOException; import java.io.Writer; import java.util.Collection; import java.util.Collections; import java.util.Comparator; import java.util.Iterator; import java.util.LinkedList; import java.util.List; import java.util.Map; /** * Base class for implementing ClusterWriter */ public abstract class AbstractClusterWriter implements ClusterWriter { private static final Logger log = LoggerFactory.getLogger(AbstractClusterWriter.class); private final Writer writer; private final Map<Integer, List<WeightedVectorWritable>> clusterIdToPoints; protected AbstractClusterWriter(Writer writer, Map<Integer, List<WeightedVectorWritable>> clusterIdToPoints) { this.writer = writer; this.clusterIdToPoints = clusterIdToPoints; } protected Writer getWriter() { return writer; } protected Map<Integer, List<WeightedVectorWritable>> getClusterIdToPoints() { return clusterIdToPoints; } public static String getTopFeatures(Vector vector, String[] dictionary, int numTerms) { List<TermIndexWeight> vectorTerms = Lists.newArrayList(); Iterator<Vector.Element> iter = vector.iterateNonZero(); while (iter.hasNext()) { Vector.Element elt = iter.next(); vectorTerms.add(new TermIndexWeight(elt.index(), elt.get())); } // Sort results in reverse order (ie weight in descending order) Collections.sort(vectorTerms, new Comparator<TermIndexWeight>() { @Override public int compare(TermIndexWeight one, TermIndexWeight two) { return Double.compare(two.weight, one.weight); } }); Collection<Pair<String, Double>> topTerms = new LinkedList<Pair<String, Double>>(); for (int i = 0; i < vectorTerms.size() && i < numTerms; i++) { int index = vectorTerms.get(i).index; String dictTerm = dictionary[index]; if (dictTerm == null) { log.error("Dictionary entry missing for {}", index); continue; } topTerms.add(new Pair<String, Double>(dictTerm, vectorTerms.get(i).weight)); } StringBuilder sb = new StringBuilder(100); for (Pair<String, Double> item : topTerms) { String term = item.getFirst(); sb.append("\n\t\t"); sb.append(StringUtils.rightPad(term, 40)); sb.append("=>"); sb.append(StringUtils.leftPad(item.getSecond().toString(), 20)); } return sb.toString(); } @Override public long write(Iterable<Cluster> iterable) throws IOException { return write(iterable, Long.MAX_VALUE); } @Override public void close() throws IOException { writer.close(); } @Override public long write(Iterable<Cluster> iterable, long maxDocs) throws IOException { long result = 0; Iterator<Cluster> iterator = iterable.iterator(); while (result < maxDocs && iterator.hasNext()) { write(iterator.next()); result++; } return result; } private static class TermIndexWeight { private final int index; private final double weight; TermIndexWeight(int index, double weight) { this.index = index; this.weight = weight; } } }