Fast convex hull

In the built-in {grDevices} package there is chull() function, which contains an alternative algorithm for calculating convex hull. It is faster compared to the sf::st_convex_hull().

Code

library("sf")
set.seed(1)

n = 2000000
df = data.frame(x = rnorm(n), y = rnorm(n))
pts = st_as_sf(df, coords = c("x", "y"))
pts = st_combine(pts)

system.time({
  ch_sf = st_convex_hull(pts)
})

##    user  system elapsed 
##    3.37    0.22    3.59

system.time({
  crds = st_coordinates(pts)
  ch_r = grDevices::chull(crds)
  ch_r = st_as_sf(df[ch_r, ], coords = c("x", "y"))
  ch_r = st_cast(st_combine(ch_r), "POLYGON")
})

##    user  system elapsed 
##    0.16    0.05    0.20

st_equals(ch_r, ch_sf, sparse = FALSE)

##      [,1]
## [1,] TRUE

plot(ch_sf, axes = TRUE, main = "Convex hull")