/*
* 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.Random;
import com.rapidminer.tools.RandomGenerator;
/**
* Creates a shuffled partition for an example set. This implementation traverses
* the partition backwards, from the last element up to the second, repeatedly
* swapping a randomly selected element into the "current position". Elements
* are randomly selected from the portion of the list that runs from the first
* element to the current position, inclusive.
*
* @author Ingo Mierswa
* @version $Id: ShuffledPartitionBuilder.java,v 2.6 2006/03/21 15:35:39
* ingomierswa Exp $
*/
public class ShuffledPartitionBuilder extends SimplePartitionBuilder {
private Random random;
public ShuffledPartitionBuilder(int seed) {
this.random = RandomGenerator.getRandomGenerator(seed);
}
/**
* Returns a shuffled partition for an example set. Uses the partition
* delivered by the superclass and shuffles the elements.
*/
public int[] createPartition(double[] ratio, int size) {
int[] part = super.createPartition(ratio, size);
// Create a random permutation of the generated array by swapping
// elements
for (int i = part.length - 1; i >= 1; i--) {
int swap = random.nextInt(i);
int dummy = part[i];
part[i] = part[swap];
part[swap] = dummy;
}
return part;
}
}