saurfang / graphcoloring

Graph Coloring Algorithms for tidygraph

graphcoloring

graphcoloring is a collection of graph coloring algorithms for coloring vertices of a graph such that no two adjacent vertices share the same color. The algorithms are included via the embedded ‘GraphColoring’ C++ library, https://github.com/brrcrites/GraphColoring.

Installation

You can install the released version of graphcoloring from CRAN with:

install.packages("graphcoloring")

Development version can be installed with

devtools::install_github("saurfang/graphcoloring")

Example

color_* functions operate under tidygraph family and can be used to color nodes within mutate context similar to group_* functions in tidygraph.

library(graphcoloring)
library(tidygraph)
library(ggraph)

set.seed(42)

play_islands(5, 10, 0.8, 3) %>%
  mutate(color = as.factor(color_dsatur())) %>%
  ggraph(., layout = 'kk') +
  geom_edge_link(aes(alpha = ..index..), show.legend = FALSE) +
  geom_node_point(aes(color = color), size = 7) +
  theme_graph()

graph_coloring_* functions directly take adjacency lists and returns an integer vector of assigned labels. For example, this can be used with sf::st_intersects() to color a feature collection for visualization.

library(graphcoloring)
library(USAboundaries)
library(sf)
library(ggplot2)

set.seed(48)

us_states() %>%  
  filter(!(name %in% c("Alaska", "District of Columbia", "Hawaii", "Puerto Rico"))) %>%
  mutate(
    color = st_intersects(.) %>%
      graph_coloring_dsatur() %>%
      as.factor()
  ) %>%
  ggplot() +
  geom_sf(aes(fill = color)) +
  theme_bw()