Fig. 4

MSE_test for AQI prediction. The first subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for NO₂ prediction. The second subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for PM₁₀ prediction. The third subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for O3 prediction. The fourth subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for PM₂₅ prediction. The fifth subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for AQI prediction on direct model. The sixth subgraph shows the MSE_test of three algorithms (CMG, SVR, NAR) for AQI prediction on composition model