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Exercise

Directed igraph objects

In this exercise you will learn how to create a directed graph from a dataframe, how to inspect whether a graph object is directed and/or weighted and how to extract those vertices at the beginning and end of directed edges.

Instructions

100 XP
  • Convert the dataframe measles into an igraph graph object using the function graph_from_data_frame() and ensure that it will be a directed graph by setting the second argument to TRUE.
  • Check if the graph object is directed by using is.directed().
  • Examine whether the edges of the graph object are already weighted by using is.weighted().
  • Subset each vertex from which each edge originates by using head_of(). This function takes two arguments, the first being the graph object and the second the edges to examine. For all edges you can use E(g).