Table 2. Stacking model evaluation.

Country	Precision	Recall	F1 score	Sample number
America	0.976	0.952	0.964	42
China	0.982	0.991	0.987	111
Denmark	0.967	0.975	0.971	120
Spain	0.991	0.981	0.986	108
Mean/Sum	0.979	0.979	0.979	381