Blue Vorontex #47

Polar Voronoi Tesselation

A Voronoi tesselation with 100 tiles in polar coordinates.

Basically - select 100 random points in a plane and then draw polygons around those points, such that all points closet to a given point, are included in the polygon associated with that point.

Those tesselations have practical uses in a number of subjects. City planning, trying to place facilities maximising access for the population.

Modelling of territorial behaviour of animal populations.

It is also found at the core of certain clustering algorithms, eg k-means clustering.

As always we need the tidyverse, and in this case the deldir package, that does the actual tesselation.

library(tidyverse)
library(deldir)

Generate random points, making sure that we can reproduce them.

set.seed(47)
tiler <- 100
x <- rnorm(tiler)
y <- rnorm(tiler)

Next, calculate the tiles, and collect them in a dataframe:

tesselation <- deldir(x, y)
tiles <- tile.list(tesselation)
points <- data.frame(x=x, y=y)
tiles_df <- lapply(tiles, function(tile){
  data.frame(x=tile$x, y = tile$y)
}) %>% 
  bind_rows(.id = "tile_id")

Next, plot it:

tiles_df %>% 
  ggplot(aes(x = x, y = y, group = tile_id, fill = tile_id)) +
  geom_polygon() +
  theme_minimal() +
  coord_polar(start = 0.47) +
  theme(legend.position = "none" ,
        axis.text = element_blank(),
        axis.title = element_blank(),
        axis.line = element_blank(),
        axis.ticks = element_blank(),
        panel.grid = element_blank()) +
        scale_fill_manual(values = hcl.colors(tiler, "Blues 3")) +
        theme(legend.position = "none")

ggsave("Blue_Vorontex-47.png")