Network chart with R and igraph: chart parameters



The igraph package is the best way to build network diagrams with R. This post describes the different parameters offered by the library, allowing to customize node, link and label features..

Network section Data to Viz

Default network chart with igraph


This post assumes you already know how to build a basic network chart with the igraph library. If you don’t have a look to the network section that provides an introduction.

Basically, igraph allows to transform several types of input into a graph object that can be plotted using the plot() function as follow:

# Library
library(igraph)

# Create data
set.seed(1)
data <- matrix(sample(0:1, 100, replace=TRUE, prob=c(0.8,0.2)), nc=10)
network <- graph_from_adjacency_matrix(data , mode='undirected', diag=F )

# Default network
par(mar=c(0,0,0,0))
plot(network)

Customize node features


Node can be modified buy several arguments that all start with vertex.. A vertex is a node in igraph language. Main options are explained in the code below:

plot(network,
    vertex.color = rgb(0.8,0.2,0.2,0.9),           # Node color
    vertex.frame.color = "Forestgreen",            # Node border color
    vertex.shape=c("circle","square"),             # One of “none”, “circle”, “square”, “csquare”, “rectangle” “crectangle”, “vrectangle”, “pie”, “raster”, or “sphere”
    vertex.size=c(15:24),                          # Size of the node (default is 15)
    vertex.size2=NA,                               # The second size of the node (e.g. for a rectangle)
    )

Customize label features


Following the same principle, options starting with vertex.label. control the labgel features. Note that when several values are provided to an option, values are used subsequently and recycled.

plot(network,
    vertex.label=LETTERS[1:10],                    # Character vector used to label the nodes
    vertex.label.color=c("red","blue"),
    vertex.label.family="Times",                   # Font family of the label (e.g.“Times”, “Helvetica”)
    vertex.label.font=c(1,2,3,4),                  # Font: 1 plain, 2 bold, 3, italic, 4 bold italic, 5 symbol
    vertex.label.cex=c(0.5,1,1.5),                 # Font size (multiplication factor, device-dependent)
    vertex.label.dist=0,                           # Distance between the label and the vertex
    vertex.label.degree=0 ,                        # The position of the label in relation to the vertex (use pi)
    )

Customize link features


Last but not least, control edges with arguments starting with edge..

plot(network,
    edge.color=rep(c("red","pink"),5),           # Edge color
    edge.width=seq(1,10),                        # Edge width, defaults to 1
    edge.arrow.size=1,                           # Arrow size, defaults to 1
    edge.arrow.width=1,                          # Arrow width, defaults to 1
    edge.lty=c("solid")                           # Line type, could be 0 or “blank”, 1 or “solid”, 2 or “dashed”, 3 or “dotted”, 4 or “dotdash”, 5 or “longdash”, 6 or “twodash”
    #edge.curved=c(rep(0,5), rep(1,5))            # Edge curvature, range 0-1 (FALSE sets it to 0, TRUE to 0.5)
    )

All customization


Of course, you can use all the options described above all together on the same chart, for a high level of customization.

par(bg="black")

plot(network, 
    
    # === vertex
    vertex.color = rgb(0.8,0.4,0.3,0.8),          # Node color
    vertex.frame.color = "white",                 # Node border color
    vertex.shape="circle",                        # One of “none”, “circle”, “square”, “csquare”, “rectangle” “crectangle”, “vrectangle”, “pie”, “raster”, or “sphere”
    vertex.size=14,                               # Size of the node (default is 15)
    vertex.size2=NA,                              # The second size of the node (e.g. for a rectangle)
    
    # === vertex label
    vertex.label=LETTERS[1:10],                   # Character vector used to label the nodes
    vertex.label.color="white",
    vertex.label.family="Times",                  # Font family of the label (e.g.“Times”, “Helvetica”)
    vertex.label.font=2,                          # Font: 1 plain, 2 bold, 3, italic, 4 bold italic, 5 symbol
    vertex.label.cex=1,                           # Font size (multiplication factor, device-dependent)
    vertex.label.dist=0,                          # Distance between the label and the vertex
    vertex.label.degree=0 ,                       # The position of the label in relation to the vertex (use pi)
    
    # === Edge
    edge.color="white",                           # Edge color
    edge.width=4,                                 # Edge width, defaults to 1
    edge.arrow.size=1,                            # Arrow size, defaults to 1
    edge.arrow.width=1,                           # Arrow width, defaults to 1
    edge.lty="solid",                             # Line type, could be 0 or “blank”, 1 or “solid”, 2 or “dashed”, 3 or “dotted”, 4 or “dotdash”, 5 or “longdash”, 6 or “twodash”
    edge.curved=0.3    ,                          # Edge curvature, range 0-1 (FALSE sets it to 0, TRUE to 0.5)
    )

Related chart types


Grouped and Stacked barplot
Treemap
Doughnut
Pie chart
Dendrogram
Circular packing



Contact

This document is a work by Yan Holtz. Any feedback is highly encouraged. You can fill an issue on Github, drop me a message on Twitter, or send an email pasting yan.holtz.data with gmail.com.

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