Social Network Analysis

Worksheet 6: Network Visualization I

Load Packages

library(igraph)
library(graphlayouts)
library(ggraph)
library(networkdata)

Prepare data

# load the game of thrones dataset
data(got)
gotS1 <- got[[1]]

Basic plotting

plot(gotS1)

Note

This plot is not representative for the capabilities of igraph. Check out this tutorial

# quick plot function of ggraph
autograph(gotS1)

autograph() allows you to specify node/edge colours too but it really is only meant to give you a quick overview without writing a massive amount of code. Think of it as the plot() function for ggraph.

Before we continue, we add some more node attributes to the GoT network that can be used during visualization.

# define a custom color palette
got_palette <- c(
  "#1A5878", "#C44237", "#AD8941", "#E99093",
  "#50594B", "#8968CD", "#9ACD32"
)

# compute a clustering for node colors
V(gotS1)$clu <- as.character(membership(cluster_louvain(gotS1)))

# compute degree as node size
V(gotS1)$size <- degree(gotS1)

Aesthetics and scales examples

ggraph(gotS1, layout = "stress") +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  geom_node_text(aes(filter = (size >= 25), label = name), size = 6) +
  scale_fill_manual(values = got_palette) +
  scale_edge_width(range = c(0.2, 3)) +
  scale_size(range = c(3, 12)) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

Using geom_edge_link instead of geom_edge_link0 for gradients along edges

ggraph(gotS1, layout = "stress") +
  geom_edge_link(aes(alpha = after_stat(index)), edge_colour = "black") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  scale_fill_manual(values = got_palette) +
  scale_edge_width_continuous(range = c(0.2, 3)) +
  scale_size_continuous(range = c(1, 6)) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

Using geom_edge_link2 instead of geom_edge_link0 for more advanced gradients along edges

ggraph(gotS1, layout = "stress") +
  geom_edge_link2(aes(edge_colour = node.clu),edge_width = 0.5)+
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  scale_fill_manual(values = got_palette) +
  scale_edge_color_manual(values = got_palette) +
  scale_edge_width_continuous(range = c(0.2, 3)) +
  scale_size_continuous(range = c(1, 6)) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

Using a different geom

ggraph(gotS1, layout = "stress") +
  geom_edge_arc0(aes(edge_width = weight), edge_colour = "grey66",strength = 0.1) +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  scale_fill_manual(values = got_palette) +
  scale_edge_width(range = c(0.2, 3)) +
  scale_size(range = c(1, 6)) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

Not specifying any scales:

ggraph(gotS1, layout = "stress") +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

ggraph(gotS1, layout = "stress") +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  scale_fill_brewer(palette = "Dark2") +
  scale_edge_width_continuous(range = c(0.2, 3)) +
  scale_size_continuous(range = c(1, 6)) +
  theme_graph() +
  theme(legend.position = "none")+
  coord_fixed()

ggraph(gotS1, layout = "stress") +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  scale_fill_manual(values = got_palette) +
  scale_edge_width_continuous(range = c(0.2, 3), guide = "none") +
  scale_size_continuous(range = c(1, 6), guide = "none") +
  theme_graph() +
  theme(legend.position = "bottom") +
  coord_fixed()

Contentric layouts

Plot that focuses on Ned Stark:

ggraph(gotS1, layout = "focus", focus = 1) +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  geom_node_text(aes(filter = (name == "Ned"), size = size, label = name),
    family = "serif"
  ) +
  scale_edge_width_continuous(range = c(0.2, 1.2)) +
  scale_size_continuous(range = c(1, 5)) +
  scale_fill_manual(values = got_palette) +
  theme_graph() +
  theme(legend.position = "none") + 
  coord_fixed()

Adding draw_circle:

ggraph(gotS1, layout = "focus", focus = 2) +
  draw_circle(col = "#00BFFF", use = "focus", max.circle = 3) +
  geom_edge_link0(aes(width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  geom_node_text(aes(filter = (name == "Daenerys"), size = size, label = name),
    family = "serif"
  ) +
  scale_edge_width_continuous(range = c(0.2, 1.2)) +
  scale_size_continuous(range = c(1, 5)) +
  scale_fill_manual(values = got_palette) +
  theme_graph() +
  theme(legend.position = "none") + 
  coord_fixed()

Concentric layout based on a centrality index:

ggraph(gotS1, layout = "centrality", cent = strength(gotS1)) +
  geom_edge_link0(aes(edge_width = weight), edge_colour = "grey66") +
  geom_node_point(aes(fill = clu, size = size), shape = 21) +
  geom_node_text(aes(size = size, label = name), family = "serif") +
  scale_edge_width_continuous(range = c(0.2, 0.9)) +
  scale_size_continuous(range = c(1, 8)) +
  scale_fill_manual(values = got_palette) +
  theme_graph() +
  theme(legend.position = "none") + 
  coord_fixed()

Exercise 1

Use the network of a different season to produce a plot by yourself
OR choose a dataset from the networkdata package data(package = "networkdata")

There are no constrains, just try out and play around

Exercise 2

Recreate the iconic “polblogs” network visualization

The network shows the linking between political blogs during the 2004 election in the US. Red nodes are conservative leaning blogs and blue ones liberal.

data("polblogs")