How can you create a Voronoi diagram in R?

2 Generate sample points

Next, you will need to generate some sample points that will serve as the centers of the Voronoi regions. You can use the randomPoints() function from the dismo package to create a set of random points within a given extent. You can specify the extent using the extent() function from the raster package, which takes the minimum and maximum coordinates of the x and y axes. For example, you can create 20 random points within an extent of (0, 10, 0, 10) with this code:

library(raster)
e <- extent(0, 10, 0, 10)
pts <- dismo::randomPoints(e, 20)        

3 Convert points to spatial object

To create a Voronoi diagram, you will need to convert the points to a spatial object that can be processed by the rgeos package. You can use the SpatialPoints() function from the sp package to do this. You can also assign a coordinate reference system (CRS) to the spatial object using the proj4string() function. For example, you can use the EPSG code 4326 for the WGS84 geographic CRS with this code:

library(sp)
sp_pts <- SpatialPoints(pts)
proj4string(sp_pts) <- CRS("+init=epsg:4326")        

4 Create Voronoi diagram

Now you are ready to create the Voronoi diagram using the gVoronoiDiagram() function from the rgeos package. This function takes a spatial object as input and returns a spatial object of class SpatialPolygons . You can also specify a buffer distance to extend the Voronoi regions beyond the extent of the points. For example, you can create a Voronoi diagram with a buffer of 1 unit with this code:

library(rgeos)
vor <- gVoronoiDiagram(sp_pts, buffer = 1)        

5 Plot Voronoi diagram

Finally, you can plot the Voronoi diagram using the ggplot() function from the ggplot2 package. This function allows you to create customized plots using layers of aesthetics and geometries. You can use the fortify() function from the ggplot2 package to convert the spatial object to a data frame that can be plotted. You can also add the points and labels to the plot using the geom_point() and geom_text() functions. For example, you can plot the Voronoi diagram with this code:

library(ggplot2)
vor_df <- fortify(vor)
ggplot(vor_df, aes(x = long, y = lat, group = group)) +
  geom_polygon(color = "black", fill = "white") +
  geom_point(data = sp_pts, aes(x = coords.x, y = coords.y)) +
  geom_text(data = sp_pts, aes(x = coords.x, y = coords.y, label = row.names(sp_pts)), size = 3) +
  coord_equal() +
  labs(title = "Voronoi diagram in R")