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In this set of exercises we shall create an empty graph and practice the functions for basic manipulation with vertices and edges, using the package `igraph`. If you don’t have the package already installed, install it using the following code:

``` install.packages("igraph") ```

and load it into the session using the following code:

``` library("igraph") ```

Answers to the exercises are available here.

If you have different solution, feel free to post it.

Exercise 1

Create an empty directed graph with 5 nodes. Set color of all nodes to yellow and shape to sphere.

Exercise 2

Add the following edges to the graph: 1->2, 1->3, 2->4, 3->4, 4->5.

Exercise 3

Add a vertex to the graph, color it to red and add edges: 3->6, 6->5. Set vertex shape to sphere.

Exercise 4

Replace edge 1->3 with the edge 3->1.

Exercise 5

Name vertices with letters A-F. List all vertices and edges.

Exercise 6

What is the shortest path between vertices A and E.

Exercise 7

Plot the graph. The size of a vertex should depend on the number of incoming edges.

Exercise 8

Plot the distribution of vertices degrees.

Exercise 9

Create a heatmap from the data.

Exercise 10

Create graph from subset of vertices with 1 or more incoming edges and plot it. Set the vertice shape to green box. The size of a vertice should depend on the number of outcoming edges.