source: branches/MetisMQI/src/main/java/weka/classifiers/meta/generators/UniformDataGenerator.java

/*
 *    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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 *   UniformDataGenerator.java
 *   Copyright (C) 2008 K.Hempstalk, University of Waikato, Hamilton, New Zealand.
 */

package weka.classifiers.meta.generators;

/**
 <!-- globalinfo-start -->
 * A uniform artificial data generator.<br/>
 * <br/>
 * This generator uses a uniform data model - all values have the same probability, and generated values must fall within the range given to the generator.
 * <p/>
 <!-- globalinfo-end -->
 *
 <!-- options-start -->
 * Valid options are: <p/>
 * 
 * <pre> -D
 *  If set, generator is run in debug mode and
 *  may output additional info to the console</pre>
 * 
 * <pre> -S &lt;seed&gt;
 *  Sets the seed of the random number generator of the generator (default: 1)</pre>
 * 
 * <pre> -L &lt;num&gt;
 *  Sets the lower range of the generator
 *  (default: 0)</pre>
 * 
 * <pre> -U &lt;num&gt;
 *  Sets the upper range of the generator
 *  (default: 1)</pre>
 * 
 <!-- options-end -->
 *
 * @author Kathryn Hempstalk (kah18 at cs.waikato.ac.nz)
 * @version $Revision: 5861 $
 */
public class UniformDataGenerator 
  extends RandomizableRangedGenerator
  implements NumericAttributeGenerator {

  /** for serialization. */
  private static final long serialVersionUID = -6390354660638644832L;

  /**
   * Returns a string describing this class' ability.
   *
   * @return A description of the class.
   */
  public String globalInfo() {
    return 
        "A uniform artificial data generator.\n"
      + "\n"
      + "This generator uses a uniform data model - all values have "
      + "the same probability, and generated values must fall within "
      + "the range given to the generator.";
  }

  /**
   * Generates a value that falls under this distribution.
   *
   * @return A generated value.
   */
  public double generate() {
    double range = (m_UpperRange - m_LowerRange);       
    return (m_Random.nextDouble() * range) + m_LowerRange;
  }

  /**
   * Gets the probability that a value falls under
   * this distribution.
   * 
   *
   * @param somedata The value to get the probability of.
   * @return The probability of the given value.
   */
  public double getProbabilityOf(double somedata) {
    double range = (m_UpperRange - m_LowerRange);
    if (range <= 0 || somedata > m_UpperRange || somedata < m_LowerRange) {
      return Double.MIN_VALUE;
    }

    return 1 / (range);
  }

  /**
   * Gets the (natural) log of the probability of a given value.
   *
   * @param somedata The value to get the log probability of.
   * @return The (natural) log of the probability.
   */ 
  public double getLogProbabilityOf(double somedata) {
    double range = (m_UpperRange - m_LowerRange);       
    if ((range <= 0) || (((somedata < m_LowerRange) || (somedata > m_UpperRange)))) {       
      return Math.log(Double.MIN_VALUE);
    }
    return -Math.log(range);
  }
}