Visualize Node Degree Distribution in a Network Graph — plot_node

Generates a horizontal bar‐style plot of node degrees for an igraph network. For undirected graphs, it shows each node’s total degree. For directed graphs, it displays in‐degrees (as negative bars) alongside out‐degrees.

Usage

plot_node_degrees(graph)

Arguments

graph: An igraph object. Can be either directed or undirected.

Value

A ggplot object:

Undirected graphs: A bar for each node showing its total degree.
Directed graphs: Split bars per node with negative values for in‐degree (pointing left) and positive values for out‐degree (pointing right).

Details

This function computes:

Total degree: Number of edges incident on each node (for undirected graphs).
In‐degree: Number of incoming edges per node (for directed graphs).
Out‐degree: Number of outgoing edges per node (for directed graphs).

For directed graphs, in‐degrees are negated so that bars extend leftward, providing an immediate visual comparison to out‐degrees.

Internally, it uses:

igraph::degree() to compute degrees,
dplyr and tidyr for reshaping the data,
ggplot2 for plotting.

Customization

You can modify the returned ggplot with additional layers, themes, or labels. For example, to add a title or change colors:


plot_node_degrees(g) +
  ggtitle("Degree Distribution") +
  scale_fill_manual(values = c("in_degree" = "steelblue", "out_degree" = "salmon"))

Examples

library(ig.degree.betweenness)
library(igraphdata)
data("karate")
data("oncology_network")
plot_node_degrees(oncology_network)

plot_node_degrees(karate)
#> This graph was created by an old(er) igraph version.
#> ℹ Call `igraph::upgrade_graph()` on it to use with the current igraph version.
#> For now we convert it on the fly...