使用 GADM shapefile 为美国地图绘制较粗的州边界和较细的县边界

Question

我之前有一篇文章是关于使用GADM中的形状文件绘制美国地图，同时删除五大湖地区的颜色映射。根据@Majid 的建议解决了该问题。

现在，我进一步想要更厚的州边界和更薄的县边界。我首先绘制县级分区统计图，然后添加额外的未填充的州/国家级边界：

library(sf)
library(tidyverse)
library(RColorBrewer) #for some nice color palettes

# US map downloaded from https://gadm.org/download_country_v3.html

# National border
us0 <- st_read("<Path>\\gadm36_USA_0.shp")
# State border
us1 <- st_read("<Path>\\gadm36_USA_1.shp")
# County border
us2 <- st_read("<Path>\\gadm36_USA_2.shp")

# Remove the Great Lakes
# retrieving the name of lakes and excluding them from the sf 
all.names = us2$NAME_2
patterns = c("Lake", "lake")

lakes.name <- unique(grep(paste(patterns, collapse="|"), 
                     all.names, 
                     value=TRUE, ignore.case = TRUE))

# Pick the Great Lakes
lakes.name <- lakes.name[c(4, 5, 7, 10, 11)]

`%notin%` <- Negate(`%in%`)
us2 <- us2[us2$NAME_2 %notin% lakes.name, ]

# National level
mainland0 <- ggplot(data = us0) +
    geom_sf(fill = NA, size = 0.3, color = "black") +
    coord_sf(crs = st_crs(2163), 
             xlim = c(-2500000, 2500000), 
             ylim = c(-2300000, 730000)) 

# State level
mainland1 <- ggplot(data = us1, size = 0.3, color = "black") +
    geom_sf(fill = NA) +
    coord_sf(crs = st_crs(2163), 
             xlim = c(-2500000, 2500000), 
             ylim = c(-2300000, 730000))

# County level
mainland2 <- ggplot(data = us2) +
    geom_sf(aes(fill = NAME_2), size = 0.1, color = "black") +
    coord_sf(crs = st_crs(2163), 
             xlim = c(-2500000, 2500000), 
             ylim = c(-2300000, 730000))+
    guides(fill = F)

# Final plot across three levels
p <- mainland2 +
    geom_sf(data = us1, fill = NA, size = 0.3, color = "black") +
    coord_sf(crs = st_crs(2163), 
             xlim = c(-2500000, 2500000), 
             ylim = c(-2300000, 730000)) +
    geom_sf(data = us0, fill = NA, size = 0.3, color = "black") +
    coord_sf(crs = st_crs(2163), 
             xlim = c(-2500000, 2500000), 
             ylim = c(-2300000, 730000)) +
    guides(fill = F)

生成的图像如下： 可以看到，虽然五大湖地区不再用颜色编码，但州边界仍然存在（红色箭头）。我想要一个如下图，其中各州由陆地边界分隔，并且没有州边界跨越湖区：

任何有关如何实现这一目标的建议都将受到赞赏。

Answer 1

你甚至不需要us0（国界）和us1（州界）。这些已经存在于us2. 您可以绘制所需的输出，如下所示：

us0 <- sf::st_union(us2)
us1 <- us2 %>% 
           group_by(NAME_1)%>% 
           summarise()

和你绘制的图：

# Final plot across three levels
p <- mainland2 +
  geom_sf(data = us1, fill = NA, size = 1.5, color = "black") +
  coord_sf(crs = st_crs(2163), 
           xlim = c(-2500000, 2500000), 
           ylim = c(-2300000, 730000)) +
  geom_sf(data = us0, fill = NA, size = 1.5, color = "black") +
  coord_sf(crs = st_crs(2163), 
           xlim = c(-2500000, 2500000), 
           ylim = c(-2300000, 730000)) +
  guides(fill = F)

p

希望有帮助。