private void validate() throws RrdException {
		boolean ok = true;
		if(x.length != y.length || x.length < 3) {
			ok = false;
		}
		for(int i = 0; i < x.length - 1 && ok; i++) {
			if(x[i] >= x[i + 1] || Double.isNaN(y[i])) {
				ok = false;
			}
		}
		if(!ok) {
			throw new RrdException("Invalid plottable data supplied");
		}
	}