ggplot2（和SF）中世界地图的整个地球多边形

绘制世界地图时，存在一个问题ggplot2：它用相同的颜色给整个背景上色，包括图中的角点实际上不是地球的一部分，请参见以下代码产生的快照（它使用前缘）sfabdggplot2版本，但问题很普遍，请参见下面提到的博客文章）：

    #install.packages("devtools")
    #devtools::install_github("tidyverse/ggplot2")
    #devtools::install_github("edzer/sfr")

    library(ggplot2)
    library(sf)
    library(rnaturalearth)
    library(dplyr)

    theme_map <- function(...) {
      theme_minimal() +
      theme(
        text = element_text(family = "Ubuntu Regular", color = "#22211d"),
        axis.line = element_blank(),
        axis.text.x = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks = element_blank(),
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),
        panel.grid.minor = element_line(color = "#ebebe5", size = 0.2),
        panel.grid.major = element_line(color = "#ebebe5", size = 0.2),
        plot.background = element_rect(fill = "#f5f5f2", color = NA),
        panel.background = element_rect(fill = "#f5f5f2", color = NA),
        legend.background = element_rect(fill = "#f5f5f2", color = NA),
        panel.border = element_blank(),
        ...
      )
    }

    crs <- "+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000 +datum=WGS84 +units=m +no_defs"
    ctrys50m <- ne_countries(scale = 50, type = "countries", returnclass = "sf") %>%
       select(iso_a3, iso_n3, admin)

    ggplot() + 
      geom_sf(data = ctrys50m, alpha = 0.15, fill="grey") +
      coord_map() +
      coord_sf(crs = crs) +
      theme_map()

为了能够很好地绘制地球的轮廓，在D3.js一个特殊的GeoJSON的type，{type: "Sphere"}已添加，看到这个线程，可以在行动中可以看出这里：它是在以下快照外部整个地球黑色边框：

The only trick I found in R/ggplot2 is the one published by Matt Strimas-Mackey, in his blog entry Mapping the Longest Commericial Flights in R, see the Bounding box and graticules section and the make_bbox and project_recenter functions.

These are quite a lot of code and I was wondering whether some sf or geom_sf code would make to a cleaner/simpler code, so I tried:

    # whole world WSG84 bounding box
    sphere <- ne_download(category = "physical", type = "wgs84_bounding_box", returnclass = "sf")
    sphere_laea <- st_transform(sphere, crs)
    ggplot() + 
      geom_sf(data = sphere, fill = "#D8F4FF") +
      coord_sf(crs = crs) +
      geom_sf(data = ctrys50m, alpha = 0.15, fill="grey") +
      coord_map() +
      coord_sf(crs = crs) +
      theme_map()

What I get is just an extra "anti-meridian" (note the line from North pole...) and no oceans filled with #D8F4FF... And the polygon is quite irregular at the bottom (the D3.js gurus did some smart adaptive resampling to increase the accuracy of projected lines...)

关于我为ggplot2世界地图获取整个世界多边形的尝试有什么想法吗？（感谢您阅读本文！）