从 R 中的地图中删除冗余区域（shapefile）

Question

我在地图上标出了几个欧洲国家，但有一些我不需要的异常值。我尝试使用类似问题中建议的不同方式将它们从我的空间 df 中删除，但它们不适用于这种情况。你能告诉我你关于删除它们的想法吗？我很感激。形状文件可用 here

编辑：我不仅需要从地图中删除这些区域，还需要从空间数据框中删除这些区域。

library(rgdal)
library(raster) 

myCountries <- c("Austria", "Belgium", "Czech Republic", "Denmark", "Estonia", "Finland",
                 "France", "Germany", "Latvia", "Hungary", "Iceland", "Ireland", "Italy",
                 "Netherlands", "Norway", "Portugal", "Poland", "Spain", "Sweden", "Switzerland",    
                 "Turkey", "United Kingdom")


countries  <- readOGR('ne_110m_admin_0_countries.shp')

eurcountries <- countries[countries$NAME_EN %in% myCountries ,]

eurcountries2<-spTransform(eurcountries, CRS("+proj=longlat +datum=NAD83"))

plot(eurcountries2)

Answer 1

我发现 SF 包比使用 SP 包更好，因为它与 ggplot2 配合得很好。然后限制 canvas 很简单，并增加了为国家着色的能力。

library(rgdal)
library(ggplot2)

myCountries <- c("Austria", "Belgium", "Czech Republic", "Denmark", "Estonia", "Finland",
                 "France", "Germany", "Latvia", "Hungary", "Iceland", "Ireland", "Italy",
                 "Netherlands", "Norway", "Portugal", "Poland", "Spain", "Sweden", "Switzerland",    
                 "Turkey", "United Kingdom")

countries  <- readOGR("C:/R/projects/ne_110m_admin_0_countries/ne_110m_admin_0_countries.shp")

eurcountries <- countries[countries$NAME_EN %in% myCountries, ]
    
eurcountries3 <- sf::st_as_sf(eurcountries)

ggplot(eurcountries3) +
  geom_sf(aes(fill = ADMIN)) +
  lims(x = c(50,-40), y = c(30, 74)) +
  guides(fill = "none") +
  theme_void()

Answer 2

以下是使用 terra（替代 raster）的方法：

myCountries <- c("Austria", "Belgium", "Czech Republic", "Denmark", "Estonia", "Finland",
                 "France", "Germany", "Latvia", "Hungary", "Iceland", "Ireland", "Italy",
                 "Netherlands", "Norway", "Portugal", "Poland", "Spain", "Sweden", "Switzerland",    
                 "Turkey", "United Kingdom")

library(terra)
countries  <- vect('ne_110m_admin_0_countries.shp')
eur <- countries[countries$NAME_EN %in% myCountries ,]

e <- ext(c(-28, 48, 35, 76)))
x <- crop(eur, e)

plot(x, "NAME_EN")

您可以交互地找到您需要的裁剪范围

 plot(eur)
 e <- draw()
 # now click on the map twice

或者交互子集，像这样：

 d <- disagg(eur)
 plot(d)
 s <- sel(d) # now draw a bounding box on the plot
 a <- aggregate(s, "NAME_EN")
 plot(a, "NAME_EN")

并且您可以将 SpatVector 对象强制转换为 sp 或 sf 类型，如下所示：

 sf <- sf::st_as_sf(x) 
 library(raster)
 sp <- as(x, "Spatial")

反之亦然：

 y <- vect(sf)

从 R 中的地图中删除冗余区域（shapefile）

Removing redundant areas from a map in R (shapefile)

r

gis

spatial

shapefile