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. 2017 Sep 20;473(2205):20170457. doi: 10.1098/rspa.2017.0457

Figure 3.

Figure 3.

PM2.5 classification trees with respect to five meteorological variables (without cumulative precipitation) in two air-quality monitoring sites, Aotizhongxin (a) and US Embassy (b), in the winter of 2016. The response PM2.5 is classified into four categories: PM2.5≤35 μg m−3 (green), 35 μg m−3<PM2.5≤75 μg m−3 (yellow), 75 μg m−3<PM2.5≤150 μg m−3 (orange) and PM2.5>150 μg m−3 (red). The four numbers inside each coloured node indicate the proportions of the four PM2.5 categories at each layer of the branch, and the percentage represents the marginal proportion of the sample at the node.