## 5 Clustering Results
**Cluster 4**: Futian-Luohu economic center--highlighted as red in Figure 8d, serving as the axis of the urban economy, such as Guomoa (Guomoa Station) and Chegongmiao (Chegongmiao Station). Note that Chegongmiao was a non-transfer station in 2013; however, as the center at Futian-Luohu economic center as well as one of the key development areas in Thirteenth Five-year Plan of Shenzhen, Chegongmiao becomes the first transfer hub of four lines in Shenzhen afterwards. **Cluster 5**: Ambiguous functional stations--highlighted as purple in Figure 8e. To be specific, they are: (1) suburb but key development area, such as exceptions mentioned in Type II; (2) Meilin-Caitian district, a key area within Meilin industrial zone in the north of Futian, which is a newly qualified key development area in the Thirteenth Five-Year Plan of Shenzhen, i.e., Shangmeilin (Shanghai Station); (3) intermediate region nearby or between development areas, such as Honglangbei (Honglang North Station) nearby high-tech zone north district. Indeed, this type of stations are generated by unstable members randomly shifting among multiple clusterings for both SFD-out and SFD-in. We have 19 outlier stations detected as listed in Table 4.  
Moreover, Figure 9 demonstrates temporal patterns in terms of in-station and out-station passenger volume for each type of stations using typical examples. From the perspective of commuting behavior, temporal pattern of passengers can be explained in the following. * Cluster 1 in Figure 9a,b: morning peak only shows in out-station flow around 08:00, while evening peak only appears in in-station flow around 18:00, indicating Xingdong station might be workplace and people commute regularly to and from work. That is, people traveling at Cluster 1 stations are likely to be commuters. * Cluster 2 in Figure 9c,d: no significant peak appears during the whole day period. Therefore, passengers at Cluster 2 stations probably exhibit random behavior. * Cluster 3 in Figure 9e,f: morning peak only shows in in-station flow around 07:00, while evening peak only appears in out-station flow around 19:00, indicating Longsheng might be place of residence. Corresponding to Figure 9a,b, people travel from residence at 07:00 to workplace at 08:00, and return from work at 18:00 to home at 19:00. Therefore, we infer that passengers at residential stations are exactly the same with those appear at workplace stations. That is, passengers at Cluster 3 stations are also regular commuters. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Station Name** & **Line Name** & **Line id** & **Station id** & **Region** \\ \hline _jichangdong_ & Luobao Line & 1 & 101 & Bao’an \\ _hourui_ & Luobao Line & 1 & 102 & Bao’an \\ _gushu_ & Luobao Line & 1 & 103 & Bao’an \\ _goutvonggyuan_ & Luobao Line & 1 & t131 & Futian \\ _slekugang_ & Shekou Line & 2 & 202 & Nanshan \\ _shuiwan_ & Shekou Line & 2 & 204 & Nanshan \\ _wanxia_ & Shekou Line & 2 & 206 & Nanshan \\ _dengliang_ & Shekou Line & 2 & 208 & Nanshan \\ _yitian_ & Longgang Line & 3 & 301 & Futian \\ _goutvonggyuan_ & Longgang Line & 3 & t131 & Futian \\ _cutizhu_ & Longgang Line & 3 & 312 & Luohu \\ _liuyue_ & Longgang Line & 3 & 320 & Longgang \\ _ailian_ & Longgang Line & 3 & 326 & Longgang \\ _shangneilin_ & Longhua Line & 4 & 407 & Futian \\ _longhua_ & Longhua Line & 4 & 414 & Longhua \\ _huangbeiling_ & Huanzhong Line & 5 & t251 & Luohu \\ _fanshen_ & Huanzhong Line & 5 & 505 & Bao’an \\ _honglanglebei_ & Huanzhong Line & 5 & 507 & Bao’an \\ _taitan_ & Huanzhong Line & 5 & 525 & Luohu \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Outlier stations of Cluster 5. * Cluster 4 in Figure 9g,h: both in-station and out-station have morning peaks and evening peaks. Specifically, the in-station morning peak is lower than in-station evening peak, and out-station shows the opposite pattern. Besides, the peak volumes are lower compared to Clusters 1 and 3. Hence, we speculate the function of Cluster 4 stations falls in between labor-intensive and densely settled area.