thomasp85/ggraph

Exterior Edge Routing

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#303 opened on Oct 27, 2021

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enhancementhelp wanted

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Description

I wondered whether it would be possible to implement something like "exterior edge routing" to improve the readability of graphs created with the hierarchical edge bundling technique; e.g.

flaregraph <- graph_from_data_frame(flare$edges, vertices = flare$vertices)

from <- match(flare$imports$from, flare$vertices$name)
to <- match(flare$imports$to, flare$vertices$name)

ggraph(flaregraph, layout = 'dendrogram', circular = TRUE) + 
    geom_conn_bundle(data = get_con(from = from, to = to), alpha = 0.1) + 
    coord_fixed()

The idea would be to route edges that are part of the same group around the exterior of a "connected circle".

This has, for instance, been used to visualize trade agreements between countries in different "trading blocks": http://ftavis.com/

Contributor guide

Research direction
Study the current hierarchical edge bundling implementation in ggraph, understand the concept of exterior edge routing from the linked example (http://ftavis.com/), and implement a new routing method that groups edges by a factor and routes them around the exterior of the circle.
Tech stack
r
Domain
data visualization
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Rggraphigraph
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25