Identifying key vertices
Perhaps the most straightforward measure of vertex importance is the degree of a vertex. The out-degree of a vertex is the number of other individuals to which a vertex has an outgoing edge directed to. The in-degree is the number of edges received from other individuals. In the measles network, individuals that infect many other individuals will have a high out-degree. In this exercise you will identify whether individuals infect equivalent amount of other children or if there are key children who have high out-degrees and infect many other children.
This exercise is part of the course
Network Analysis in R
Exercise instructions
- Calculate the out-degree of each vertex using the function
degree(). The first argument is the network graph object and the second argument is themodewhich should be one ofout,inorall. Assign the output of this function to the objectg.outd. - View a summary of the out-degrees of all individuals using the function
table()on the vector objectg.outd. - Make a histogram of the out-degrees using the function
hist()on the vector objectg.outd. - Determine which vertex has the highest out-degree in the network using the function
which.max()on the vector objectg.outd.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
library(igraph)
# Calculate the out-degree of each vertex
___ <- ___(g, mode = c("___"))
# View a summary of out-degree
___(g.outd)
# Make a histogram of out-degrees
___(g.outd, breaks = 30)
# Find the vertex that has the maximum out-degree
___(g.outd)