Dendrogram customization with R and ggraph

This post follows the previous introduction to ggraph and dendrogram. It shows how to customize the dendrogram: layout, edge style, node features and more.

Dendrogram section Data to Viz

Start by creating a dataset and a graph object using the igraph package.

# Libraries
# data: edge list
d1 <- data.frame(from="origin", to=paste("group", seq(1,7), sep=""))
d2 <- data.frame(from=rep(d1$to, each=7), to=paste("subgroup", seq(1,49), sep="_"))
edges <- rbind(d1, d2)
# We can add a second data frame with information for each node!
name <- unique(c(as.character(edges$from), as.character(edges$to)))
vertices <- data.frame(
  group=c( rep(NA,8) ,  rep( paste("group", seq(1,7), sep=""), each=7)),
  cluster=sample(letters[1:4], length(name), replace=T),
  value=sample(seq(10,30), length(name), replace=T)
# Create a graph object
mygraph <- graph_from_data_frame( edges, vertices=vertices)

Circular or linear layout

First of all, you can use a linear or a circular representation using the circular option thanks to the layout argument of ggraph.

Note: a customized version of the circular dendrogram is available here, with more node features and labels.

# Left
ggraph(mygraph, layout = 'dendrogram', circular = FALSE) + 
# Right
ggraph(mygraph, layout = 'dendrogram', circular = TRUE) + 

Edge style

Then you can choose between different styles for your edges. The ggraph package comes with 2 main functions: geom_edge_link and geom_edge_diagonal.

Note that the most usual “elbow” representation is not implemented for hierarchical data yet.

# Left
ggraph(mygraph, layout = 'dendrogram') + 
# Right
ggraph(mygraph, layout = 'dendrogram') + 

Labels and Nodes

You probably want to add labels to give more insight to your tree. And eventually nodes. This can be done using the geom_node_text and geom_node_point respectively.

Note: the label addition is a bit more tricky for circular dendrogram, a solution is suggested in graph #339.

# Left
ggraph(mygraph, layout = 'dendrogram') + 
  geom_edge_diagonal() +
  geom_node_text(aes( label=name, filter=leaf) , angle=90 , hjust=1, nudge_y = -0.01) +
  ylim(-.4, NA)
# Right
ggraph(mygraph, layout = 'dendrogram') + 
  geom_edge_diagonal() +
  geom_node_text(aes( label=name, filter=leaf) , angle=90 , hjust=1, nudge_y = -0.04) +
  geom_node_point(aes(filter=leaf) , alpha=0.6) +
  ylim(-.5, NA)

Customize aesthetics

It is a common task to add color or shapes to your dendrogram. It allows to show more clearly the organization of the dataset.

ggraph works the same way as ggplot2. In the aesthetics part of each component, you can use a column of your initial data frame to be mapped to a shape, a color, a size or other..

ggraph(mygraph, layout = 'dendrogram') + 
  geom_edge_diagonal() +
  geom_node_text(aes( label=name, filter=leaf, color=group) , angle=90 , hjust=1, nudge_y=-0.1) +
  geom_node_point(aes(filter=leaf, size=value, color=group) , alpha=0.6) +
  ylim(-.6, NA) +

Related chart types

Grouped and Stacked barplot
Pie chart
Circular packing


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 with

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