PL4246 Networks in Psychology: Tutorial 1

Video 1: Varieties of Network Types

Set up

library(igraph)
library(igraphdata)

load('data/examples_for_videos.RData') # loads the networks we will use 

Network with undirected, unweighted edges

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_ud_uw) # the default plot 

We can improve it! (or not…)

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_ud_uw,
     vertex.color = 'darkorchid1',
     vertex.frame.color = 'lightgrey',
     vertex.label.dist = 1.7,
     vertex.label.family = 'sans', 
     edge.color = 'darkolivegreen', 
     edge.width = 1.5,
     edge.curved = 0.5) 

Network with undirected, weighted edges

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_ud_w) # the default plot does not show the weights!

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_ud_w, edge.width = E(g_ud_w)$weight) # to adjust widths with the weights 

Network with directed, unweighted edges

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_d_uw) # the arrows are naturally provided in directed graphs 

The arrows can also be tweaked.

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_d_uw,
     edge.arrow.width = 0.5,
     edge.arrow.size = 1.5,
     edge.color = 'limegreen')

Network with directed, weighted edges

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_d_w) # again, notice the weighted edges are not showing up

par(mar=c(0,0,0,0)+.1) # to reduce the margins around the graph
plot(g_d_w, 
     edge.width = E(g_d_w)$weight,
     edge.arrow.width = 2)

Network layouts

data("karate") # we need a more complicated graph to show the different layouts 

par(mar=c(0,0,0,0)+.3, mfrow = c(1,2)) # to reduce the margins around the graph + plot both networks together
set.seed(1) # to fix graph layout 

plot(karate, layout = layout_in_circle, main = 'circle')
plot(karate, layout = layout_with_gem, main = "gem")