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.
   */
  
  /*
   *    SplitEvaluate.java
   *    Copyright (C) 2000 University of Waikato, Hamilton, New Zealand
   *    
   */
  
  package weka.classifiers.trees.m5;
  
  import weka.core.Instances;
  
  /**
   * Interface for objects that determine a split point on an attribute
   *
   * @author Mark Hall (mhall@cs.waikato.ac.nz)
   * @version $Revision: 1.3 $
   */
  public interface SplitEvaluate {
    
    /**
     * makes a copy of the SplitEvaluate object
     * @return a copy of the object
     */
    SplitEvaluate copy () throws Exception;
  
    /** 
     * Finds the best splitting point for an attribute in the instances
     * @param attr the splitting attribute
     * @param inst the instances
     * @exception Exception if something goes wrong
     */
     void attrSplit (int attr, Instances inst) throws Exception;
  
    /**
     * Returns the impurity of this split
     *
     * @return the impurity of this split
     */
     double maxImpurity();
  
    /**
     * Returns the position of the split in the sorted values. -1 indicates that
     * a split could not be found.
     *
     * @return an <code>int</code> value
     */
     int position();
    
    /**
     * Returns the attribute used in this split
     *
     * @return the attribute used in this split
     */
     int splitAttr();
  
    /**
     * Returns the split value
     *
     * @return the split value
     */
     double splitValue();
  
  }
  