code: ///////////////////////////////////////////////////////////////////////////////
  // For information as to what this class does, see the Javadoc, below.       //
  // Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
  // 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
  // Ramsey, and Clark Glymour.                                                //
  //                                                                           //
  // This program 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 2 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 General Public License for more details.                              //
  //                                                                           //
  // You should have received a copy of the GNU General Public License         //
  // along with this program; if not, write to the Free Software               //
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
  ///////////////////////////////////////////////////////////////////////////////
  
  package edu.cmu.tetrad.data;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * Provides a static method for sampling without replacement from a dataset to
   * create a new dataset with a sample size supplied by the user.
   *
   * @author Frank Wimberly
   */
  public final class RandomSampler {
  
      /**
       * This method takes a dataset and a sample size and creates a new dataset
       * containing that number of samples by drawing with replacement from the
       * original dataset.
       */
      public static DataSet sample(DataSet dataSet,
                                   int newSampleSize) {
          if (newSampleSize < 1) {
              throw new IllegalArgumentException("Sample size must be > 0.");
          }
  
          if (dataSet.getNumRows() < 1) {
              throw new IllegalArgumentException("Dataset must contain samples.");
          }
  
          if (dataSet.getNumRows() < newSampleSize) {
              throw new IllegalArgumentException("Not enough cases in data to " +
                      "generate " + newSampleSize + " samples without replacement.");
          }
  
          List<Integer> indices = new ArrayList<>(dataSet.getNumRows());
  
          for (int i = 0; i < dataSet.getNumRows(); i++) {
              indices.add(i);
          }
  
          Collections.shuffle(indices);
  
          //Number of samples in input dataset
          int ncols = dataSet.getNumColumns();
  
          DataSet newDataSet =
                  new ColtDataSet(newSampleSize, dataSet.getVariables());
  
          for (int i = 0; i < newSampleSize; i++) {
              int oldCase = indices.get(i);
  
              for (int j = 0; j < ncols; j++) {
                  newDataSet.setObject(i, j, dataSet.getObject(oldCase, j));
              }
          }
  
          return newDataSet;
      }
  }
  
  
  
  