TransactionDatabaseGenerator.java

package ca.pfv.spmf.tools.dataset_generator;

/* This file is copyright (c) 2008-2012 Philippe Fournier-Viger
* 
* This file is part of the SPMF DATA MINING SOFTWARE
* (http://www.philippe-fournier-viger.com/spmf).
* 
* SPMF is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later
* version.
* SPMF 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 General Public License for more details.
* You should have received a copy of the GNU General Public License along with
* SPMF. If not, see <http://www.gnu.org/licenses/>.
*/

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Random;

/**
* This class is a random transaction database generator such that the user provides some parameters and this class generate a transaction database
* that is written to the disk.
* 

* @author Philippe Fournier-Viger
*/
public class TransactionDatabaseGenerator {

	// the random number generator
	private static Random random = new Random(System.currentTimeMillis());

	/**
	 * This method randomly generates a transaction database according to parameters provided.
	 * @param transactionCount transaction count the number of transactions required
	 * @param maxDistinctItems the maximum number of distinct items
	 * @param maxItemCountPerTransaction the maximum number of items per transaction
	 * @param output the file path for writting the generated database
	 * @throws IOException 
	 */
	public  void generateDatabase(int transactionCount, int maxDistinctItems, int maxItemCountPerTransaction,
			String output) throws IOException {
		
		// We create a BufferedWriter to write the database to disk
		BufferedWriter writer = new BufferedWriter(new FileWriter(output)); 
		// For the number of transactions to be generated
		for (int i = 0; i < transactionCount; i++) {
			// if it is not the first one, we write on a new line
			if(i != 0){
				writer.newLine();
			}
			// We randomly decide how many items will appear in this transaction
			int itemCount = random.nextInt(maxItemCountPerTransaction) + 1;
			
			// This hashset will be used to remember which items have
			// already been added to this itemset.
			HashSet<Integer> alreadyAdded = new HashSet<Integer>();
			
			// create an arraylist to store items from the itemset that will be generated
			List<Integer> itemset = new ArrayList<Integer>();
			// for the number of items that was decided above
			for (int j = 0; j < itemCount; j++) {
				// we generate the item randomly and write it to disk
				int item = random.nextInt(maxDistinctItems) + 1;
				// if we already added this item to this itemset
				// we choose another one
				while(alreadyAdded.contains(item)){
					item = random.nextInt(maxDistinctItems) + 1;
				}
				alreadyAdded.add(item);
				itemset.add(item);
			}
			// sort the itemset
			Collections.sort(itemset);
			// write the itemset
			for(int j=0; j< itemset.size(); j++){
				if(j != 0){
					writer.write(" ");
				}
				writer.write(""+itemset.get(j));
			}
			
		}
		writer.close(); // close the file.
	}
}