Research Article
Using the Quarterly Compound Fractional Grey Model to Predict the Air Quality in 22 Cities of China
Table 2
The fitting results of NO2 concentration by three models in Tangshan (unit: μg/m3).
| Quarter | Actual value | GM (1, 1) | FGM (1, 1) | QCGM (1, 1) |
| 2015-1 | 68 | 68 | 68 | 68 | 2015-2 | 54 | 60 | 55 | 54 | 2015-3 | 50 | 59 | 56 | 49 | 2015-4 | 68 | 59 | 57 | 69 | 2016-1 | 61 | 58 | 58 | 66 | 2016-2 | 52 | 58 | 59 | 54 | 2016-3 | 47 | 57 | 59 | 48 | 2016-4 | 73 | 57 | 59 | 67 | 2017-1 | 68 | 56 | 58 | 64 | 2017-2 | 56 | 56 | 58 | 52 | 2017-3 | 50 | 55 | 57 | 46 | 2017-4 | 61 | 55 | 57 | 64 | 2018-1 | 56 | 54 | 56 | 60 | 2018-2 | 49 | 54 | 55 | 49 | 2018-3 | 41 | 53 | 54 | 43 | 2018-4 | 60 | 53 | 53 | 60 | 2019-1 | 56 | 52 | 52 | 57 | 2019-2 | 44 | 52 | 51 | 46 | 2019-3 | 42 | 51 | 50 | 41 | 2019-4 | 59 | 51 | 49 | 56 | MAPE (%) | | 13.47 | 12.89 | 4.09 |
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