/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.com
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.example.set;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import com.rapidminer.example.Attribute;
import com.rapidminer.example.Attributes;
import com.rapidminer.example.Example;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.example.Statistics;
import com.rapidminer.example.table.ExampleTable;
/**
* <p>This example set uses a mapping of indices to access the examples provided by the
* parent example set. The mapping does not need to contain unique indices which is
* especially useful for sampling with replacement. For performance reasons (iterations,
* database access...) the mapping will be sorted during the construction of this example
* set (based on the parameter sort).</p>
*
* <p>Please note that the constructor takes a boolean flag indicating if the examples
* from the given array are used or if the examples which are not part of this mapping
* should be used. This might be useful in the context of bootstrapped validation for
* example.</p>
*
* @author Ingo Mierswa, Martin Scholz
* @version $Id: MappedExampleSet.java,v 1.7 2008/05/09 19:22:49 ingomierswa Exp $
*/
public class MappedExampleSet extends AbstractExampleSet {
private static final long serialVersionUID = -488025806523583178L;
/** The parent example set. */
private ExampleSet parent;
/** The used mapping. */
private int[] mapping;
/** Constructs an example set based on the given mapping. */
public MappedExampleSet(ExampleSet parent, int[] mapping) {
this(parent, mapping, true);
}
/** Constructs an example set based on the given mapping. If the boolean flag
* useMappedExamples is false only examples which are not part of the original
* mapping are used. */
public MappedExampleSet(ExampleSet parent, int[] mapping, boolean useMappedExamples) {
this(parent, mapping, useMappedExamples, true);
}
/** Constructs an example set based on the given mapping. If the boolean flag
* useMappedExamples is false only examples which are not part of the original
* mapping are used. If the boolean flag sort is false the mapping is used as is.*/
public MappedExampleSet(ExampleSet parent, int[] mapping, boolean useMappedExamples, boolean sort) {
this.parent = (ExampleSet)parent.clone();
this.mapping = mapping;
if(sort) Arrays.sort(this.mapping);
if (!useMappedExamples) {
List<Integer> inverseIndexList = new ArrayList<Integer>();
int currentExample = -1;
for (int m : mapping) {
if (m != currentExample) {
for (int z = currentExample + 1; z < m; z++) {
inverseIndexList.add(z);
}
currentExample = m;
}
}
this.mapping = new int[inverseIndexList.size()];
Iterator<Integer> i = inverseIndexList.iterator();
int index = 0;
while (i.hasNext())
this.mapping[index++] = i.next();
}
}
/** Clone constructor. */
public MappedExampleSet(MappedExampleSet exampleSet) {
this.parent = (ExampleSet)exampleSet.parent.clone();
this.mapping = exampleSet.mapping;
}
public boolean equals(Object o) {
if (!super.equals(o))
return false;
if (!(o instanceof MappedExampleSet))
return false;
MappedExampleSet other = (MappedExampleSet)o;
if (this.mapping.length != other.mapping.length)
return false;
for (int i = 0; i < this.mapping.length; i++)
if (this.mapping[i] != other.mapping[i])
return false;
return true;
}
public int hashCode() {
return super.hashCode() ^ this.mapping.hashCode();
}
/** Returns a {@link MappedExampleReader}. */
public Iterator<Example> iterator() {
return new MappedExampleReader(parent.iterator(), this.mapping);
}
/** Returns the i-th example in the mapping. */
public Example getExample(int index) {
if ((index < 0) || (index >= this.mapping.length)) {
throw new RuntimeException("Given index '" + index + "' does not fit the mapped ExampleSet!");
} else {
return parent.getExample(this.mapping[index]);
}
}
/** Counts the number of examples. */
public int size() {
return mapping.length;
}
public Attributes getAttributes() {
return parent.getAttributes();
}
public ExampleTable getExampleTable() {
return parent.getExampleTable();
}
/** Creates a new mapping for the given example set by sampling with replacement. */
public static int[] createBootstrappingMapping(ExampleSet exampleSet, int size, Random random) {
int[] mapping = new int[size];
for (int i = 0; i < mapping.length; i++)
mapping[i] = random.nextInt(exampleSet.size());
return mapping;
}
public static int[] createWeightedBootstrappingMapping(ExampleSet exampleSet, int size, Random random) {
Attribute weightAttribute = exampleSet.getAttributes().getSpecial(Attributes.WEIGHT_NAME);
exampleSet.recalculateAttributeStatistics(weightAttribute);
double maxWeight = exampleSet.getStatistics(weightAttribute, Statistics.MAXIMUM);
int[] mapping = new int[size];
for (int i = 0; i < mapping.length; i++) {
int index = -1;
do {
index = random.nextInt(exampleSet.size());
Example example = exampleSet.getExample(index);
double currentWeight = example.getValue(weightAttribute);
if (random.nextDouble() > currentWeight / maxWeight) {
index = -1;
}
} while (index == -1);
mapping[i] = index;
}
return mapping;
}
}