equalitysplitter.java

Boosting算法软件包

/** EqualitySplitter
 *  Splits the data based on testing a discrete attribute
 *  for equality with some value
 *
 * @author Nigel Duffy
 */
package jboost.learner;
import jboost.examples.Attribute;
import jboost.examples.AttributeDescription;
import jboost.examples.DiscreteAttribute;
import jboost.examples.Instance;

/**
 * Splits examples according to whether a {@link jboost.examples.RealAttribute} is equal to a fixed value.
 * If it is equal, returns 0 or -1 if unknown or 1 if not equal and split is binary.
 */
class EqualitySplitter extends Splitter {
    private int value;

   /** Does this need to be public?					*/
    public int getValue() {return(value);}

    public EqualitySplitter(int ind,int v,int deg,AttributeDescription attr) {
	index=ind;
	value=v;
	if(deg>2 ||deg<1) throw(new RuntimeException("Equality Splitter defined with inappropriate degree:"+deg));
	degree=deg;
	desc=attr;
	m_type= SplitterType.EQUALITY_SPLITTER;
	}

/**
 * Return the partition in which an instance belongs. 
 * returning -1 signifies "partition unknown". 
 * If the attribute is equal to the desired value,
 * then return 0.
 * If the split is binary and the attribute is not equal, then return 1.
 * 
 * Inherited from Splitter
 */
    public int eval(Instance instance) throws IncompAttException {
	Attribute t=instance.getAttribute(index);
	if(t == null) {return(-1);}
	try {
	    DiscreteAttribute a= (DiscreteAttribute) t;	// try downcasting 
	    if(a.getValue()==value) return(0);
	    else if(degree==2) return(1);
	    else throw(new RuntimeException("Equality Split with degree greater than 2"));
	}
	catch (ClassCastException e) {
	    throw new IncompAttException("InequalitySplitter Error:",index
					 ,t.getClass());
	}
    }

    /** Produce a copy */
    public Object clone() {
	EqualitySplitter retval=new EqualitySplitter(index,value,degree,desc);
	return(retval);
    } 

    /** Returns a string describing this splitter */
    public String toString() {
	String retval=new String("EqualitySplit: "+degree);
	try{
		retval+=" "+desc.getAttributeName()+" = "+desc.getAttributeValue(value);
	} catch(Exception e) {retval=null;}
	return(retval);
    }

  /** Produces a java implementation of this splitter.				*/
   public String toC(String fname) {return(null);}

  /** Produces a java implementation of this splitter.				*/
   public String toJava(String fname) {
	String retval="\tprivate int "+fname+"(Instance ins){\n";
	retval+="\t\tif(((DiscreteAttribute)ins.getAttribute("+index+")).getValue()=="+value+") return(0);\n";
	retval+="\t\telse return(1);\n";
	retval+="\t}\n\n";
	return(retval);
   }

    public boolean equals(Splitter sp) {
        EqualitySplitter isp;
        try{isp=(EqualitySplitter)sp;}
        catch(ClassCastException e) {
                return(false);
        }
        if(index==isp.index && value==isp.value) return(true);
        else return(false);
    }

   /** Get a summary.                                                   */
    public Summary getSummary() {
        Summary retval=new Summary();
        retval.index=index;
        retval.type=Summary.EQUALITY;
        retval.val = new Integer(value);
        return(retval);
    }
}