ggraph (version 0.1.1)

geom_edge_bundle: Create heirarchical edge bundles between nodes

Description

Hierarchical edge bundling is a technique to introduce some order into the hairball structure that can appear when there's a lot of overplotting and edge crossing in a network plot. The concept requires that the network has an intrinsic hierarchical structure that defines the layout but is not shown. Connections between points (that is, not edges) are then drawn so that they loosely follows the underlying hierarchical structure. This results in a flow-like structure where lines that partly move in the same direction will be bundled togeether.

Usage

geom_edge_bundle(mapping = NULL, data = gCon(), position = "identity", arrow = NULL, lineend = "butt", show.legend = NA, n = 100, tension = 0.8, ...)
geom_edge_bundle2(mapping = NULL, data = gCon(), position = "identity", arrow = NULL, lineend = "butt", show.legend = NA, n = 100, tension = 0.8, ...)
geom_edge_bundle0(mapping = NULL, data = gCon(), position = "identity", arrow = NULL, lineend = "butt", show.legend = NA, tension = 0.8, ...)

Arguments

mapping

Set of aesthetic mappings created by aes or aes_. By default x, y, xend, yend, group and circular are mapped to x, y, xend, yend, edge.id and circular in the edge data.

data

The result of a call to gCon

position

Position adjustment, either as a string, or the result of a call to a position adjustment function.

arrow

Arrow specification, as created by arrow

lineend

Line end style (round, butt, square)

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes.

n

The number of points to create along the path.

tension

How "loose" should the bundles be. 1 will give very tight bundles, while 0 will turn of bundling completely and give straight lines. Defaults to 0.8

...

other arguments passed on to layer. These are often aesthetics, used to set an aesthetic to a fixed value, like color = "red" or size = 3. They may also be parameters to the paired geom/stat.

Aesthetics

geom_edge_bundle* understands the following aesthetics. Bold aesthetics are automatically set, but can be overridden.

• x
• y
• group
• circular
• edge_colour
• edge_width
• edge_linetype
• edge_alpha
• filter

Computed variables

References

Holten, D. (2006). Hierarchical edge bundles: visualization of adjacency relations in hierarchical data. IEEE Transactions on Visualization and Computer Graphics, 12(5), 741-748. http://doi.org/10.1109/TVCG.2006.147

See Also

Other geom_edge_*: geom_edge_arc, geom_edge_density, geom_edge_diagonal, geom_edge_elbow, geom_edge_fan, geom_edge_hive, geom_edge_link, geom_edge_loop

Examples

# Create a graph of the flare class system
library(igraph)
flareGraph <- graph_from_data_frame(flare$edges, vertices = flare$vertices)
importFrom <- match(flare$imports$from, flare$vertices$name)
importTo <- match(flare$imports$to, flare$vertices$name)
flareGraph <- treeApply(flareGraph, function(node, parent, depth, tree) {
    tree <- set_vertex_attr(tree, 'depth', node, depth)
    if (depth == 1) {
        tree <- set_vertex_attr(tree, 'class', node, V(tree)$shortName[node])
    } else if (depth > 1) {
        tree <- set_vertex_attr(tree, 'class', node, V(tree)$class[parent])
    }
    tree
})
V(flareGraph)$leaf <- degree(flareGraph, mode = 'out') == 0

# Use class inheritance for layout but plot class imports as bundles
ggraph(flareGraph, 'dendrogram', circular = TRUE) +
    geom_edge_bundle(aes(colour = ..index..), data = gCon(importFrom, importTo),
                     edge_alpha = 0.25) +
    geom_node_point(aes(filter = leaf, colour = class)) +
    scale_edge_colour_distiller('', direction = 1, guide = 'edge_direction') +
    coord_fixed() +
    ggforce::theme_no_axes()