void normalize() {
		for(int i = 0; i < cols(); i++) {
			if(valueCount(i) == 0) {
				double min = columnMin(i);
				double max = columnMax(i);
				for(int j = 0; j < rows(); j++) {
					double v = get(j, i);
					if(v != MISSING)
						set(j, i, (v - min) / (max - min));
				}
			}
		}
	}