NumericalSplitter.java example

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rapidminer-5-master
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package com.rapidminer.operator.learner.tree;

import java.util.Iterator;

import com.rapidminer.example.Attribute;
import com.rapidminer.example.Example;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.example.set.SortedExampleSet;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.operator.learner.tree.criterions.Criterion;
import com.rapidminer.tools.Tools;

/**
 * Calculates the best split point for numerical attributes according to 
 * a given criterion.
 * 
 * @author Ingo Mierswa
 */
public class NumericalSplitter {
	
    private Criterion criterion;
    
    
    public NumericalSplitter(Criterion criterion) {
        this.criterion = criterion;
    }
    
    public double getBestSplit(ExampleSet inputSet, Attribute attribute) throws OperatorException {
        SortedExampleSet exampleSet = new SortedExampleSet((ExampleSet)inputSet.clone(), attribute, SortedExampleSet.INCREASING);
        // Attribute labelAttribute = exampleSet.getAttributes().getLabel(); // see bug report 952
        //double oldLabel = Double.NaN; // see bug report 952
        double bestSplit = Double.NaN;
        double lastValue = Double.NaN;
        double bestSplitBenefit = Double.NEGATIVE_INFINITY;
      
        Example lastExample = null;
        if (this.criterion.supportsIncrementalCalculation()) {
        	this.criterion.startIncrementalCalculation(exampleSet);
        }
        
        Iterator<Example> exampleIterator = exampleSet.iterator();
        while(exampleIterator.hasNext()) {
        	Example e = exampleIterator.next();
        	//boolean isLast = !(exampleIterator.hasNext()); // see bug report 952
        	double currentValue = e.getValue(attribute);
        	
        	// double label = e.getValue(labelAttribute);  // see bug report 952
    		if (this.criterion.supportsIncrementalCalculation()) {
    			if (lastExample != null) 
    				this.criterion.swapExample(lastExample);
    			lastExample = e;
    			//if ((Double.isNaN(oldLabel)) || (oldLabel != label) || isLast) {  // see bug report 952
    			//if ((Double.isNaN(oldLabel)) || (oldLabel != label)) {  // see bug report 952
    			if (!Tools.isEqual(currentValue, lastValue)) {
    				double benefit = this.criterion.getIncrementalBenefit();

    				if (benefit > bestSplitBenefit) {
    					bestSplitBenefit = benefit;
    					bestSplit = (lastValue + currentValue) / 2.0d;
    				}
    				// oldLabel = label; // see bug report 952
    			}
        		//} // see bug report 952
        	//} else if ((Double.isNaN(oldLabel)) || (oldLabel != label)) {  // see bug report 952
    		} else {  
        		if (!Tools.isEqual(currentValue, lastValue)) {
        			double splitValue = (lastValue + currentValue) / 2.0d;
        			double benefit = this.criterion.getNumericalBenefit(exampleSet, attribute, splitValue);
        			if (benefit > bestSplitBenefit) {
        				bestSplitBenefit = benefit;
        				bestSplit = splitValue;
        			}
        			// oldLabel = label; // see bug report 952
        		}
        	}
    		
            lastValue = currentValue;
        }
        return bestSplit;
    }
}