Prediction of China’s Sulfur Dioxide Emissions by Discrete Grey Model with Fractional Order Generation Operators

Table 2

The fitted values and MAPE of different discrete grey models.

Sequence	Sample data	Geometric shape of sequence	Models	MAPE (%)
		Up, convex	Direct modeling
					Up, concave	Direct modeling
								Down, convex	Direct modeling
		Down, concave							Direct modeling
					Strict nonhomogeneous				Direct modeling
								Approximate nonhomogeneous	Direct modeling