nemo

nemo finds the largest empty circle in the plane whose interior does not overlap with any given obstacles. nemo includes ony two functions :

• nemo_hull computes a concave hull from a set of points and is basically imported from package concaveman brought in R by joelgombin
• nemo_circle computes the larget circle inside a hull and which doesn’t include any point : its center will be the point nemo

Installation

You can install the development version from GitHub with:

## install {remotes} if not already
if (!requireNamespace("remotes")) {
  install.packages("remotes")
}
## install nemo for github
remotes::install_github("mtmx/nemo")

Example

A basic example to find the largest empty circle inside a set of points and its center aka the point nemo :

library(nemo)
data(points)
hull_pts <-
nemo_hull(points = points %>% st_transform(2154),
            concavity =2,
            length_threshold = 10)

nemo_pts <-
nemo_circle(points = points %>% st_transform(2154),
            hull = hull_pts %>% st_buffer(dist=500),
            strict_inclusion = T,
            nmax_circles = 1)
#> Warning: attribute variables are assumed to be spatially constant
#> throughout all geometries

# mapping output
library(ggplot2)

ggplot() +
  geom_sf(data = hull_pts %>% st_buffer(dist=500)  , size = 0.2) +
  geom_sf(data = nemo_pts ,
          size = 1,
          fill=NA,
          color = "red") +
  geom_sf(data = nemo_pts %>% st_centroid() ,
             size = 1,
             col = "red") +
  geom_sf(data=points %>% st_transform(2154))
#> Warning in st_centroid.sf(.): st_centroid assumes attributes are constant
#> over geometries of x