In arc2r/book: All things R Spatial or A guide to spatial R for Recovering ArcGIS Users

set.seed(10)
mypoints <- data.frame(x = rnorm(1000),y = rnorm(1000)) %>%
  st_as_sf(coords = c(1,2))

plot(mypoints)

my_kde <- function(points,cellsize, bandwith, extent = NULL){
  require(MASS)
  require(raster)
  require(sf)
  if(is.null(extent)){
    extent_vec <- st_bbox(points)[c(1,3,2,4)]
  } else{
    extent_vec <- st_bbox(extent)[c(1,3,2,4)]
  }

  n_y <- ceiling((extent_vec[4]-extent_vec[3])/cellsize)
  n_x <- ceiling((extent_vec[2]-extent_vec[1])/cellsize)

  extent_vec[2] <- extent_vec[1]+(n_x*cellsize)-cellsize
  extent_vec[4] <- extent_vec[3]+(n_y*cellsize)-cellsize

  coords <- st_coordinates(points)
  matrix <- kde2d(coords[,1],coords[,2],h = bandwith,n = c(n_x,n_y),lims = extent_vec)
  raster(matrix)
}

mypoints_kde <- my_kde(mypoints,0.01,1)
library(stars)

ggplot() +
  geom_stars(data = st_as_stars(mypoints_kde)) +
  geom_sf(data = mypoints, alpha = 0.2, fill = "black") +
  scale_fill_viridis_c() +
  labs(fill = "KDE") +
  theme_void() 

arc2r/book documentation built on March 5, 2021, 2:10 p.m.