public NegativeBinomial(int r, double p) throws ParameterException {
		if (r < 1 || p < 0 || p > 1) {
			throw new ParameterException("Negative binomial r >= 1, 0 <= p <= 1.");
		} else {
			this.r = r;
			this.p = p;
			geom = new Geometric(1 - p);
		}
	}