CODEWITHSUNDEEP
rgisgeospatialr-sfvoronoi
Mark R
Mark R

Reputation: 1009

merge st_voronoi polygons by variable

I'd like to create polygons with st_voronoi and merge them by a variable

library(sf)
nc_centroids <- st_transform(nc_centroids,crs=32119)
nc_centroids$foo <- c(rep("green",50),rep("red",50))
nc <- st_transform(nc,crs=32119)
v <- st_voronoi(st_union(nc_centroids))
plot(v, col = 0)
plot(st_intersection(st_cast(v), st_union(nc)), col = 0) 
plot(nc_centroids, add = TRUE)

How might I merge the polygons in v by nc_centroids$foo to create two big polygons? I can think of some hacks, like using lapply to join the individual polygons of v, e.g., (v[[1]][[x]]). But surely there's something easier

Upvotes: 2

Views: 334

Answers (1)

lovalery
lovalery

Reputation: 4652

Please find below a reprex that details one possible approach.

Reprex

  • Code
library(sf)
library(dplyr)

nc <- st_read(system.file("shape/nc.shp", package="sf"))
nc_centroids <- st_centroid(nc)
nc_centroids <- st_transform(nc_centroids,crs=32119)
nc_centroids$foo <- c(rep("green",50),rep("red",50))
nc <- st_transform(nc,crs=32119)
v <- st_voronoi(st_union(nc_centroids))


v <- v %>% 
  st_collection_extract(., "POLYGON") %>% 
  st_as_sf()

v_result <- v %>% 
  st_join(., nc_centroids, st_intersects) %>% 
  group_by(foo) %>% 
  summarize()

nc_result <- nc %>% 
  st_join(., v_result) %>% 
  group_by(foo) %>% 
  summarize()
  • Output
plot(nc_result)

Created on 2022-02-07 by the reprex package (v2.0.1)

Upvotes: 4

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