samoa-api/src/main/java/org/apache/samoa/moa/classifiers/core/splitcriteria/SplitCriterion.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.samoa.moa.classifiers.core.splitcriteria;

import org.apache.samoa.moa.options.OptionHandler;

/**
 * Interface for computing splitting criteria. with respect to distributions of class values. The split criterion is
 * used as a parameter on decision trees and decision stumps. The two split criteria most used are Information Gain and
 * Gini.
 * 
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public interface SplitCriterion extends OptionHandler {

  /**
   * Computes the merit of splitting for a given ditribution before the split and after it.
   * 
   * @param preSplitDist
   *          the class distribution before the split
   * @param postSplitDists
   *          the class distribution after the split
   * @return value of the merit of splitting
   */
  public double getMeritOfSplit(double[] preSplitDist,
      double[][] postSplitDists);

  /**
   * Computes the range of splitting merit
   * 
   * @param preSplitDist
   *          the class distribution before the split
   * @return value of the range of splitting merit
   */
  public double getRangeOfMerit(double[] preSplitDist);
}