label.java

Boosting算法软件包

package jboost.examples;

/** Holds the label of an example */
public class Label extends MultiDiscreteAttribute {

    /** constructor
        @param value label's value
    */
    public Label(int v) {
	super(v);
    }

    /** constructor
        @param values array of {0,1} boolean values indicating
           membership in each class
    */
    public Label(boolean[] values) {
	super(values);
    }

    /**
     * Computes a loss for a predicted Label relative to this Label.
     * Specifically, the loss is 1 minus the number of classes at the
     * intersection of the two Label's, divided by the number of
     * classes in the predicted Label.  (An exception occurs if no
     * classes in the predicted Label.)
     */
    public double lossOfPrediction(Label p) {
	if (p.value >= 0)
	    return (getMultiValue(p.value) ? 0.0 : 1.0);
	else {
	    int num_plus = 0;
	    int num_overlap = 0;
	    for (int i = 0; i < p.values.length; i++) {
		if (p.values[i]) {
		    num_plus++;
		    if (getMultiValue(i))
			num_overlap++;
		}
	    }
	    if (num_plus == 0)
		throw new IllegalArgumentException("label must have at " +
                                "least one class in Label.lossOfPrediction");
	    return (num_plus - num_overlap) / ((double) num_plus);
	}
    }
}