r - r 按百分比用颜色填充地图

Question

如何按国家面积百分比填充地图图。

例子

library(sp)
library(raster)


# https://gadm.org/download_country_v3.html level-0
ger.shape <- readRDS("gadm36_DEU_0_sp.rds")
plot(ger.shape, col = 'lightgrey', border = 'darkgrey')
raster(extent(ger.shape))

标签： rpolygonfillshapefilearea

Answer 1

这可能是一种非常低效的方法，但这是一个开始：

library(sf)

# increment in metres.
# Smaller numbers will give you a more accurate map, but will take longer to calculate
increment <- 10*1000

# load shapefile and convert to an equal-area projection so we can work in metres
gerShp <- st_read('gadm36_DEU_shp/gadm36_DEU_0.shp') # change this to the correct path
gerShp <- st_transform(gerShp, 3035)

# calculate total area and our 30% value
totalArea <- st_area(gerShp)
thirtyPC <- totalArea * 0.3

# Plot it
plot(gerShp, col = 'lightgrey', border = 'darkgrey', max.plot=1, reset=F)

# Find the bounding box of the feature
bbox <- st_bbox(gerShp)

thisArea <- totalArea - totalArea # zero with correct units
i <- 1

# While our subarea is less than 30%...
while (thisArea < thirtyPC) {

    # Starting at bottom, create a bounding box that is smaller than full bounding box
    thisBBox <- bbox
    thisBBox['ymax'] <- thisBBox$ymin + (increment * i)

    # Clip shp to this bounding box
    thisSubarea <- st_crop(gerShp, y=thisBBox)
    thisArea <- st_area(thisSubarea)

    print(thisArea)

    i <- i + 1

}

plot(thisSubarea, max.plot=1, add=T, col='red', border=NA)
actualPercentage <- thisArea / totalArea

实际百分比 = 0.3011579