001/** 
002 * Copyright (c) 2007-2009, Regents of the University of Colorado 
003 * All rights reserved.
004 * 
005 * Redistribution and use in source and binary forms, with or without
006 * modification, are permitted provided that the following conditions are met:
007 * 
008 * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 
009 * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 
010 * Neither the name of the University of Colorado at Boulder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. 
011 * 
012 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
013 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
014 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
015 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
016 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
017 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
018 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
019 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
020 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
021 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
022 * POSSIBILITY OF SUCH DAMAGE. 
023 */
024package org.cleartk.ml.encoder.features;
025
026import java.util.ArrayList;
027import java.util.List;
028
029import org.cleartk.ml.Feature;
030import org.cleartk.ml.encoder.features.normalizer.NameNumberNormalizer;
031import org.cleartk.ml.encoder.features.normalizer.NoOpNormalizer;
032import org.cleartk.ml.feature.Counts;
033
034/**
035 * <br>
036 * Copyright (c) 2009, Regents of the University of Colorado <br>
037 * All rights reserved.
038 * 
039 * Encodes a Counts feature into a bag-of-words type feature.
040 * 
041 * This works on arbitrary types of objects, not just words. If an object's count is larger than
042 * zero, the corresponding value (named using the .toString method of the object) is set to 1. If
043 * the count is zero, the value is not included in the output.
044 * 
045 * @author Philipp Wetzler
046 */
047public class BagEncoder implements FeatureEncoder<NameNumber> {
048
049  private static final long serialVersionUID = -5280514188425612793L;
050
051  public BagEncoder(String identifier, NameNumberNormalizer normalizer) {
052    this.identifier = identifier;
053    this.normalizer = normalizer;
054  }
055
056  public BagEncoder(String identifier) {
057    this(identifier, new NoOpNormalizer());
058  }
059
060  public BagEncoder(NameNumberNormalizer normalizer) {
061    this(null, normalizer);
062  }
063
064  public BagEncoder() {
065    this(null, new NoOpNormalizer());
066  }
067
068  public List<NameNumber> encode(Feature feature) {
069    List<NameNumber> fves = new ArrayList<NameNumber>();
070    Counts frequencies = (Counts) feature.getValue();
071
072    String prefix = frequencies.getFeatureName();
073    for (Object key : frequencies.getValues()) {
074      if (frequencies.getCount(key) > 0) {
075        String name = Feature.createName(prefix, key.toString());
076        NameNumber fve = new NameNumber(name, 1);
077        fves.add(fve);
078      }
079    }
080
081    normalizer.normalize(fves);
082
083    return fves;
084  }
085
086  public boolean encodes(Feature feature) {
087    if (!(feature.getValue() instanceof Counts))
088      return false;
089
090    Counts counts = (Counts) feature.getValue();
091
092    if (identifier == null)
093      return true;
094
095    if (identifier.equals(counts.getIdentifier()))
096      return true;
097
098    return false;
099  }
100
101  private String identifier;
102
103  private NameNumberNormalizer normalizer;
104
105}