用R中的地图边界划定voronoi图

Question

我有一组纬度和经度点，我设法用它绘制了一个 voronoi 图。

我想在新加坡的 shapefile 上叠加 voronoi 图，并用地图的边界划定 voronoi 图。

我的voronoi图是：

coords <- data.frame(Lat=c(1.29370,1.37640,1.25600,1.38370,1.38240,1.31910),Long=c(103.8125,103.8492,103.6790,103.8860,103.7603,103.8191))

library(deldir)
library(ggplot2)

#This creates the voronoi line segments
voronoi <- deldir(coords$Long, coords$Lat)

#Now we can make a plot

ggplot(data=coords, aes(x=Long,y=Lat)) +
  #Plot the voronoi lines
  geom_segment(
    aes(x = x1, y = y1, xend = x2, yend = y2),
    size = 2,
    data = voronoi$dirsgs,
    linetype = 1,
    color= "#FFB958") + 
  #Plot the points
  geom_point(
    fill=rgb(70,130,180,255,maxColorValue=255),
    pch=21,
    size = 4,
    color="#333333")

我的地图是：

library(raster)
sg <- getData(country="SGP", level=0) 

如何在地图上绘制 voronoi 图并通过地图的边界对其进行划分？

Answer 1

您可以使用dismo::voronoi 后跟raster::intersect

library(dismo)
library(rgeos)

coords <- data.frame(Lat=c(1.29370,1.37640,1.25600,1.38370,1.38240,1.31910),Long=c(103.8125,103.8492,103.6790,103.8860,103.7603,103.8191))
sg <- getData(country="SGP", level=0) 

创建 Voronoi 图

v <- voronoi(coords[, c('Long', 'Lat')], ext=extent(sg)+.1)

与多边形相交

sgv <- v * sg
# or # sgv <- instersect(v, sg)

用于绘图

plot(sgv)

或者

g <- gmap(sg, lonlat=TRUE, scale=2)
plot(g, interpolate=TRUE)
lines(sgv, col='red')

Answer 2

也许这会给你一些想法：

library(deldir)
library(ggplot2)
library (ggmap)

coords <- data.frame(
    lat=c(1.29370, 1.37640, 1.25600, 1.38370, 1.38240, 1.31910),
    lon=c(103.8125, 103.8492, 103.6790, 103.8860, 103.7603, 103.8191)
    )

voronoi <- deldir(coords$lon, coords$lat)

singapore.map <- get_map("singapore", zoom=11)

ggmap(singapore.map, extent = "normal")+
  geom_segment(
    aes(x=x1, y=y1, xend=x2, yend=y2),
    size=2,
    data=voronoi$dirsgs,
    linetype=1,
    color= "#FFB958")+ 
  geom_point(
    fill=rgb(70, 130, 180, 255, maxColorValue=255),
    pch=21,
    size=4,
    color="#333333")