# DyEgoVis: Visual Exploration of Dynamic Ego-Network Evolution
## 5 Case Studies
### Enron Email Network  
Enron Corporation used to be a famous American energy company. However, it went bankrupt on 3 December 2001 due to financial scandals. The Enron email network is a dynamic network constructed based on Enron Corporation's email dataset, consisting of 141 nodes and 4473 edges. It describes email exchanges (edges) among 141 employees (nodes) during the 24 months between March 2000 and February 2002. We take a month as a timestep. Therefore, an ego-network snapshot describes the email exchanges between the ego and other employees in the month. The weight of an edge in the snapshot is the number of email exchanges between its two nodes. In the entire network, the attributes of each node include the position, the number of monthly email contacts, the total number of monthly emails, etc. There are mainly ten positions from upper-level employees to low-level employees: CEO, President, Vice President, Director, Managing Director, Manager, In House Lawyer, Trader, Employee (junior employees) and Unknown (unknown employees). After the system loads the data of the whole timespan (i.e., [March 2000, February 2002]), we select the color scheme to encode employees' positions. The higher the position of an employee is, the darker the color of the corresponding node (or point) is. In this case study, one-level alters are more meaningful than two-level alters, so we show only one-level alters in the dynamic ego-network view. After learning that Enron's stock price began to rise rapidly in July 2000 and continued to fall shortly thereafter, we adjust the timespan to [July 2000, February 2002] by using the timespan slider (T3). We select t-SNE as our project method and then click the refresh icon to reload the data of the current timespan. The embedded results (points) of the dynamic ego-networks of 141 employees (as egos) are shown in Figure 5(a). There is a small cluster (**a1**) in the view. Through examining the details of each point in this cluster, we find they have similar sparse feature sequences, as shown at the bottom in the view. This evolution pattern reveals that their egos did not communicate frequently with others between July 2000 and February 2002 (T1). Next, we want to investigate Enron's senior executives. With the help of the system's search box, we find the four CEOs: [PERSON] (founder of Enron), [PERSON] (second in command of Enron), [PERSON] (CEO of Enron North America) and [PERSON] (CEO of Enron America). However, the embedded results of their dynamic ego-networks (highlighted in red) are far away from each other (Figure 5(a)). This means that their dynamic ego-networks have different evolution patterns (T1). In addition, this can reflect that these CEOs play different roles in the company's decision-making. We then focus on the dynamic ego-networks of the two most influential CEOs [PERSON] and [PERSON] to get insight into their relationships with others. All the states of their dynamic ego-networks are shown in Figure 5(b). We notice that [PERSON]'s state b2 in August 2001 is an apparent outlier. The timesteps of the states b1 and b3 are July 2001  
Figure 6: The embedded results of the dynamic ego-networks of 141 Enron employees are displayed in (**a**) the overview view. The points in the cluster (**a1**) have similar sparse feature sequences. The four CEOs (red) have different evolution patterns. [PERSON] and [PERSON] are further investigated. All states of their dynamic ego-networks are shown in (**b**) the state view. The state sequence bone-b2-b3 reveals an abnormal change. and September 2001, respectively. The state sequence b1-b2-b3 reveals that [PERSON]'s dynamic ego-network changed dramatically between July 2001 and September 2001 (T4). To further understand these states, we drag the timeline to investigate the layouts of the corresponding snapshots in the dynamic ego-network view. As shown in Figure 7, [PERSON] (row 6, col 4) communicated with a large number of employees (i.e., one-level alters) via email in August 2001.