7.1 The Basics

suppressPackageStartupMessages(library(igraph))
suppressPackageStartupMessages(library(tidygraph))
suppressPackageStartupMessages(library(ggraph))
suppressPackageStartupMessages(library(tidyverse))

Visualization and statistics are the primary tools at our disposable for conveying convincing stories about the structure and dynamics of the networks we study.

Load data and create an igraph object from edgelist

#read data
data_url <- "https://raw.githubusercontent.com/mahoffman/social_network_analysis/master/Data/money_edgelist.csv"
money_edgelist <- read_csv(data_url)

## Rows: 11 Columns: 2
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr (2): Ego, Alter
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

#igraph
moneyNetwork_ig <- money_edgelist %>% 
  as.matrix() %>% 
  graph_from_edgelist(directed=TRUE)
#tidygraph
moneyNetwork_tg <- as_tbl_graph(moneyNetwork_ig)

money_edgelist

## # A tibble: 11 × 2
##    Ego   Alter
##    <chr> <chr>
##  1 Greg  Maria
##  2 Greg  Mark 
##  3 Greg  Lexi 
##  4 Greg  Grace
##  5 Greg  Nick 
##  6 Maria Mark 
##  7 Maria Lexi 
##  8 Maria Grace
##  9 Maria Nick 
## 10 Mark  Nick 
## 11 Lexi  Nick

moneyNetwork_ig

## IGRAPH f4a5967 DN-- 6 11 -- 
## + attr: name (v/c)
## + edges from f4a5967 (vertex names):
##  [1] Greg ->Maria Greg ->Mark  Greg ->Lexi  Greg ->Grace Greg ->Nick 
##  [6] Maria->Mark  Maria->Lexi  Maria->Grace Maria->Nick  Mark ->Nick 
## [11] Lexi ->Nick

moneyNetwork_tg

## # A tbl_graph: 6 nodes and 11 edges
## #
## # A directed acyclic simple graph with 1 component
## #
## # A tibble: 6 × 1
##   name 
##   <chr>
## 1 Greg 
## 2 Maria
## 3 Mark 
## 4 Lexi 
## 5 Grace
## 6 Nick 
## #
## # A tibble: 11 × 2
##    from    to
##   <int> <int>
## 1     1     2
## 2     1     3
## 3     1     4
## # ℹ 8 more rows

Basic igraph plot

set.seed(1992)
plot(moneyNetwork_ig)

set.seed(1992)
plot(moneyNetwork_ig)

Save “nice” layout

nt_layout <- layout_nicely(moneyNetwork_ig)

Set the layout

plot(moneyNetwork_ig, layout = nt_layout)

Basic ggraph plot

ggraph(moneyNetwork_tg, layout = nt_layout) + 
  geom_edge_link() + 
  geom_node_point()

## Warning: Using the `size` aesthetic in this geom was deprecated in ggplot2 3.4.0.
## ℹ Please use `linewidth` in the `default_aes` field and elsewhere instead.
## This warning is displayed once every 8 hours.
## Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
## generated.

7.1.1 Nodes

We can control the size of the nodes

plot(moneyNetwork_ig, layout = nt_layout, vertex.size = 50)

plot(moneyNetwork_ig, layout = nt_layout, vertex.size = 10)

ggraph(moneyNetwork_tg, layout = nt_layout) + 
  geom_edge_link() + 
  geom_node_point(size = 5)

ggraph(moneyNetwork_tg, layout = nt_layout) + 
  geom_edge_link() + 
  geom_node_point(size = 10)

We can also control the color of the nodes and their frames

plot(moneyNetwork_ig,
     layout = nt_layout,
     vertex.size = 10,
     vertex.color = "tomato",
     vertex.frame.color = NA #remove the frames of the nodes
     )

ggraph(moneyNetwork_tg, layout = nt_layout) + 
  geom_edge_link() + 
  geom_node_point(color = "tomato", size = 5)

Adjust label size with vertex.label.cex. We can adjust the color with vertex.label.color

plot(moneyNetwork_ig,
     layout = nt_layout,
     vertex.size = 10,
     vertex.color = "tomato",
     vertex.frame.color = NA,
     vertex.label.cex = .7, #adjust label size
     vertex.label.color = "black" #adjust label color
     )

ggraph(moneyNetwork_tg, layout = nt_layout) + 
  geom_edge_link() + 
  geom_node_point(color = "tomato", size = 5)+
  geom_node_text(aes(label = name))

Alternatively, if we want to get rid of the labels, we can just set vertex.label to NA.

plot(moneyNetwork_ig,
     layout = nt_layout,
     vertex.size = 10,
     vertex.color = "tomato",
     vertex.frame.color = NA,
     vertex.label = NA#remove label
     )