001 /*
002 * Created on Apr 9, 2005
003 *
004 */
005 package aima.learning.framework;
006
007 /**
008 * @author Ravi Mohan
009 *
010 */
011 import java.util.Hashtable;
012 import java.util.Iterator;
013 import java.util.LinkedList;
014 import java.util.List;
015
016 import aima.util.Util;
017
018 public class DataSet {
019 protected DataSet() {
020
021 }
022
023 public List<Example> examples;
024
025 public DataSetSpecification specification;
026
027 public DataSet(DataSetSpecification spec) {
028 examples = new LinkedList<Example>();
029 this.specification = spec;
030 }
031
032 public void add(Example e) {
033 examples.add(e);
034 }
035
036 public int size() {
037 return examples.size();
038 }
039
040 public Example getExample(int number) {
041 return examples.get(number);
042 }
043
044 public DataSet removeExample(Example e) {
045 DataSet ds = new DataSet(specification);
046 for (Example eg : examples) {
047 if (!(e.equals(eg))) {
048 ds.add(eg);
049 }
050 }
051 return ds;
052 }
053
054 public double getInformationFor() {
055 String attributeName = specification.getTarget();
056 Hashtable<String, Integer> counts = new Hashtable<String, Integer>();
057 for (Example e : examples) {
058
059 String val = e.getAttributeValueAsString(attributeName);
060 if (counts.containsKey(val)) {
061 counts.put(val, counts.get(val) + 1);
062 } else {
063 counts.put(val, 1);
064 }
065 }
066
067 double totalTargetAttributeCount = 0;
068
069 double[] data = new double[counts.keySet().size()];
070 Iterator<Integer> iter = counts.values().iterator();
071 for (int i = 0; i < data.length; i++) {
072 data[i] = iter.next();
073 }
074 data = Util.normalize(data);
075
076 return Util.information(data);
077 }
078
079 public Hashtable<String, DataSet> splitByAttribute(String attributeName) {
080 Hashtable<String, DataSet> results = new Hashtable<String, DataSet>();
081 for (Example e : examples) {
082 String val = e.getAttributeValueAsString(attributeName);
083 if (results.containsKey(val)) {
084 results.get(val).add(e);
085 } else {
086 DataSet ds = new DataSet(specification);
087 ds.add(e);
088 results.put(val, ds);
089 }
090 }
091 return results;
092 }
093
094 public double calculateGainFor(String parameterName) {
095 Hashtable<String, DataSet> hash = splitByAttribute(parameterName);
096 double totalSize = examples.size();
097 double remainder = 0.0;
098 for (String parameterValue : hash.keySet()) {
099 double reducedDataSetSize = hash.get(parameterValue).examples
100 .size();
101 remainder += (reducedDataSetSize / totalSize)
102 * hash.get(parameterValue).getInformationFor();
103 }
104 return getInformationFor() - remainder;
105 }
106
107 @Override
108 public boolean equals(Object o) {
109 if (this == o) {
110 return true;
111 }
112 if ((o == null) || (this.getClass() != o.getClass())) {
113 return false;
114 }
115 DataSet other = (DataSet) o;
116 return examples.equals(other.examples);
117 }
118
119 @Override
120 public int hashCode() {
121 return 0;
122 }
123
124 public Iterator<Example> iterator() {
125 return examples.iterator();
126 }
127
128 public DataSet copy() {
129 DataSet ds = new DataSet(specification);
130 for (Example e : examples) {
131 ds.add(e);
132 }
133 return ds;
134 }
135
136 public List<String> getAttributeNames() {
137 return specification.getAttributeNames();
138 }
139
140 public String getTargetAttributeName() {
141 return specification.getTarget();
142 }
143
144 public DataSet emptyDataSet() {
145 return new DataSet(specification);
146 }
147
148 /**
149 * @param specification
150 * The specification to set. USE SPARINGLY for testing etc ..
151 * makes no semantic sense
152 */
153 public void setSpecification(DataSetSpecification specification) {
154 this.specification = specification;
155 }
156
157 public List<String> getPossibleAttributeValues(String attributeName) {
158 return specification.getPossibleAttributeValues(attributeName);
159 }
160
161 public DataSet matchingDataSet(String attributeName, String attributeValue) {
162 DataSet ds = new DataSet(specification);
163 for (Example e : examples) {
164 if (e.getAttributeValueAsString(attributeName).equals(
165 attributeValue)) {
166 ds.add(e);
167 }
168 }
169 return ds;
170 }
171
172 public List<String> getNonTargetAttributes() {
173 return Util.removeFrom(getAttributeNames(), getTargetAttributeName());
174 }
175
176 }