In this assignment, we’ll use the krack_full data to generate
various network visualizations.
You need to complete the following tasks:
1. visualize friendship ties only

2. visualize reports-to ties only, and try different layout
options

3. plot the reports-to network; color nodes by department, and set
the vertex size by tenure

4. In addition to plotting the reports-to network, incorporate
additional tie types.
- use the layout generated by the reports-to ties but overlay the
advice and friendship ties in red and blue.
- edge attributes can be queried through E(..), and you can set edge
color of a graph by calling E(graph)$color
