samoa-api/src/main/java/com/yahoo/labs/samoa/learners/classifiers/trees/SplitNode.java

package com.yahoo.labs.samoa.learners.classifiers.trees;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2013 Yahoo! Inc.
 * %%
 * Licensed 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.
 * #L%
 */

import com.yahoo.labs.samoa.moa.classifiers.core.conditionaltests.InstanceConditionalTest;
import com.yahoo.labs.samoa.moa.core.AutoExpandVector;
import com.yahoo.labs.samoa.instances.Instance;

/**
 * SplitNode represents the node that contains one or more questions in the decision tree model,
 * in order to route the instances into the correct leaf.
 * @author Arinto Murdopo
 *
 */
public class SplitNode extends Node {
	
	private static final long serialVersionUID = -7380795529928485792L;
	
	private final AutoExpandVector<Node> children;
	protected final InstanceConditionalTest splitTest;
	
	public SplitNode(InstanceConditionalTest splitTest, 
			double[] classObservation) {
		super(classObservation);
		this.children = new AutoExpandVector<>();
		this.splitTest = splitTest;
	}

	@Override
	FoundNode filterInstanceToLeaf(Instance inst, SplitNode parent, int parentBranch) {
		int childIndex = instanceChildIndex(inst);
		if(childIndex >= 0){
			Node child = getChild(childIndex);
			if(child != null){
				return child.filterInstanceToLeaf(inst, this, childIndex);
			}
			return new FoundNode(null, this, childIndex);
		}
		return new FoundNode(this, parent, parentBranch);
	}

	@Override
	boolean isLeaf() {
		return false;
	}
	
	@Override
	double[] getClassVotes(Instance inst, ModelAggregatorProcessor vht) {
		return this.observedClassDistribution.getArrayCopy();
	}		
	
	/**
	 * Method to return the number of children of this split node
	 * @return number of children
	 */
	int numChildren(){
		return this.children.size();
	}
	
	/**
	 * Method to set the children in a specific index of the SplitNode with the appropriate child
	 * @param index Index of the child in the SplitNode
	 * @param child The child node
	 */
	void setChild(int index, Node child){
        if ((this.splitTest.maxBranches() >= 0)
                && (index >= this.splitTest.maxBranches())) {
            throw new IndexOutOfBoundsException();
        }
        this.children.set(index, child);
	}
	
	/**
	 * Method to get the child node given the index
	 * @param index The child node index
	 * @return The child node in the given index
	 */
	Node getChild(int index){
		return this.children.get(index);
	}
	
	/**
	 * Method to route the instance using this split node
	 * @param inst The routed instance
	 * @return The index of the branch where the instance is routed
	 */
	int instanceChildIndex(Instance inst){
		return this.splitTest.branchForInstance(inst);
	}
}