content: /*
   *    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.
   */
  
  /*
   *    NominalItem.java
   *    Copyright (C) 2010 University of Waikato, Hamilton, New Zealand
   *
   */
  
  package weka.associations;
  
  import java.io.Serializable;
  
  import weka.core.Attribute;
  
  
  /**
   * Class that encapsulates a nominal item.
   * 
   * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
   * @version $Revision: 6543 $
   */
  public class NominalItem extends Item implements Serializable {
  
    /** For serialization */
    private static final long serialVersionUID = 2182122099990462066L;
    
    /** The index of the value considered to be positive */
    protected int m_valueIndex;
    
    /**
     * Constructs a new NominalItem.
     * 
     * @param att the attribute that backs the item.
     * @param valueIndex the index of the value for this item.
     * @throws Exception if the NominalItem can't be constructed.
     */
    public NominalItem(Attribute att, int valueIndex) throws Exception {
      
      super(att);
      
      if (att.isNumeric()) {
        throw new Exception("NominalItem must be constructed using a nominal attribute");
      }
      m_attribute = att;
      if (m_attribute.numValues() == 1) {
        m_valueIndex = 0; // unary attribute (? used to indicate absence from a basket)
      } else {
        m_valueIndex = valueIndex;
      }
    }
    
    /**
     * Get the value index for this item.
     * 
     * @return the value index.
     */
    public int getValueIndex() {
      return m_valueIndex;
    }
    
    /**
     * Get this item's value as a String.
     * 
     * @return this item's value as a String.
     */
    public String getItemValueAsString() {
      return m_attribute.value(m_valueIndex);
    }
    
    /**
     * Get this item's comparison operator as a String.
     * 
     * @return this item's comparison operator as a String.
     */
    public String getComparisonAsString() {
      return "=";
    }
      
    /**
     * A string representation of this item, (i.e.
     * <attribute name> <comparison operator> <item value>).
     * This default implementation just prints the attribute
     * name and (optionally) frequency information.
     * 
     * @param freq true if the frequency should be included.
     * @return a string representation of this item. 
     */
    public String toString(boolean freq) {
      String result = m_attribute.name() + "=" + m_attribute.value(m_valueIndex);
      if (freq) {
        result += ":" + m_frequency;
      }
      return result;
    }
    
    /**
     * Equals. Just compares attribute and valueIndex.
     * @return true if this NominalItem is equal to the argument.
     */
    public boolean equals(Object compareTo) {
      if (!(compareTo instanceof NominalItem)) {
        return false;
      }
      
      NominalItem b = (NominalItem)compareTo;
      if (m_attribute.equals(b.getAttribute()) && 
  //        m_frequency == b.getFrequency() && 
          m_valueIndex == b.getValueIndex()) {
        return true;
      }
      
      return false;
    }
  }
  