Plotting degree distribution with igraph and ggplot2

igraph-degree-distribution.R

library("igraph")
library("poweRlaw")
library("ggplot2")

# Just loading my data
edge_list <- read.csv("edge-list-ocupacoes.csv")
G <- graph.data.frame(edge_list)

# List of degrees
G.degrees <- degree(G)

# Let's count the frequencies of each degree
G.degree.histogram <- as.data.frame(table(G.degrees))

# Need to convert the first column to numbers, otherwise
# the log-log thing will not work (that's fair...)
G.degree.histogram[,1] <- as.numeric(G.degree.histogram[,1])

# Now, plot it!
ggplot(G.degree.histogram, aes(x = G.degrees, y = Freq)) +
  geom_point() +
  scale_x_continuous("Degree\n(nodes with this amount of connections)",
                     breaks = c(1, 3, 10, 30, 100, 300),
                     trans = "log10") +
  scale_y_continuous("Frequency\n(how many of them)",
                     breaks = c(1, 3, 10, 30, 100, 300, 1000),
                     trans = "log10") +
  ggtitle("Degree Distribution (log-log)") +
  theme_bw()

Hi Ruliana,
I found that
as.numeric(G.degree.histogram[,1])
does not convert the factor degree values to correct numerical values. You may have to use
as.numeric( paste(G.degree.histogram[,1]))

Paramjit Gill

Very useful!