private double getGiniIndex(ClassificationCounter cc) { double sum = 0.0d; for (Map.Entry<Serializable, Double> e : cc.getCounts().entrySet()) { double error = (cc.getTotal() > 0) ? e.getValue() / cc.getTotal() : 0; sum += error * error; } return 1.0d - sum; }
@Override public double scoreSplit(ClassificationCounter a, ClassificationCounter b) { ClassificationCounter parent = ClassificationCounter.merge(a, b); double parentGiniIndex = getGiniIndex(parent); double aGiniIndex = getGiniIndex(a) * a.getTotal() / parent.getTotal(); double bGiniIndex = getGiniIndex(b) * b.getTotal() / parent.getTotal(); return parentGiniIndex - aGiniIndex - bGiniIndex; }