/**
* Copyright (C) 2001-2017 by RapidMiner and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapidminer.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 com.rapidminer.tools.RandomGenerator;
import java.util.Random;
/**
* 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
*/
public class ShuffledPartitionBuilder extends SimplePartitionBuilder {
private Random random;
public ShuffledPartitionBuilder(boolean useLocalRandomSeed, int seed) {
this.random = RandomGenerator.getRandomGenerator(useLocalRandomSeed, seed);
}
/**
* Returns a shuffled partition for an example set. Uses the partition delivered by the
* superclass and shuffles the elements.
*/
@Override
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;
}
}