从gglpot2地图中删除南极洲

Question

我正在尝试重现本教程，了解如何绘制类似散点图的地图。下面是完整的代码和输出：

library(readr)
library(dplyr)
library(DT)

datatable(rladies, rownames = FALSE,
          options = list(pageLength = 5))
url_csv <- 'https://raw.githubusercontent.com/d4tagirl/R-Ladies-growth-maps/master/rladies.csv'
rladies <- read_csv(url(url_csv)) %>% 
  select(-1)

library(ggplot2)
library(maps)
library(ggthemes)

world <- ggplot() +
  borders("world", colour = "gray85", fill = "gray80") +
  theme_map() 

map <- world +
  geom_point(aes(x = lon, y = lat, size = followers),
             data = rladies, 
             colour = 'purple', alpha = .5) +
  scale_size_continuous(range = c(1, 8), 
                        breaks = c(250, 500, 750, 1000)) +
  labs(size = 'Followers')

我想从地图上删除南极洲，这样它就不会占用太多空白空间。我尝试遵循另一个类似的 Stackoverflow 问题的解决方案，如下所示：

world <- map_data("world") %>% 
     filter(region != "Antarctica") %>% 
     ggplot(aes(long, lat, group = paste(region, group))) + 
     geom_polygon() + 
     coord_fixed()

map <- world +
  geom_point(aes(x = lon, y = lat, size = followers),
             data = rladies, 
             colour = 'purple', alpha = .5) +
  scale_size_continuous(range = c(1, 8), 
                        breaks = c(250, 500, 750, 1000)) +
  labs(size = 'Followers')

但是当我尝试显示地图时，出现以下错误：

粘贴错误（区域，组）：找不到对象“区域”

还有其他方法可以去除南极洲吗？

---

更新：失败

subset

尝试

countries <- map_data("world")
map_df <- subset(countries, region != "Antarctica")
map_base <- ggplot(data = map_df, mapping = aes(x = long, y = lat, group = group)) + coord_fixed(1.3) + geom_polygon(color = "black", fill = "gray")
# The base map is created successfully but I cannot plot points on it
map_base + geom_point(aes(x = lon, y = lat, size = followers), data = rladies, colour = 'purple', alpha = .5)

错误：

eval(expr, envir, enclos) 中的错误：未找到对象“组”

Answer 1

根据 hrbmstr 的建议，这里是一个使用正确投影和 sf 包（使用 ggplot2 开发版本中的 geom_sf ）的解决方案。请注意，我们使用 coord_sf 来设置限制。

library(sf)

world <- map_data("world")
world.sf <- sf::st_as_sf(world, coords = c("long", "lat"), crs = 4326) %>% 
  group_by(group) %>% 
  summarize(do_union = FALSE) %>%
  st_cast("POLYGON") %>% 
  ungroup()

world <- ggplot() +
  geom_sf(data = world.sf, colour = "gray85", fill = "gray80") + 
  coord_sf(ylim = c(-50, 90), datum = NA) +
  theme(panel.background = element_rect(fill = 'white'))

 world +
  geom_point(aes(x = lon, y = lat, size = followers),
             data = rladies, 
             colour = 'purple', alpha = .5) +
  scale_size_continuous(range = c(1, 8), 
                        breaks = c(250, 500, 750, 1000)) +
  labs(size = 'Followers', x = NULL, y = NULL)

Answer 2

我们还可以使用

coord_cartesian(ylim = c(-50, 90))

来设置 y 限制。

library(ggplot2)
library(maps)
library(ggthemes)

world <- ggplot() +
  borders("world", colour = "gray85", fill = "gray80") +
  theme_map() +
  coord_cartesian(ylim = c(-50, 90)) 


map <- world +
  geom_point(aes(x = lon, y = lat, size = followers),
             data = rladies, 
             colour = 'purple', alpha = .5) +
  scale_size_continuous(range = c(1, 8), 
                        breaks = c(250, 500, 750, 1000)) +
  labs(size = 'Followers')

map

Answer 3

这是另一种方法，它使用过滤器和一行代码来使用其 3 字母代码删除南极洲：

library( tidyverse )
library( cowplot )
library( sf )
library( lwgeom )
library( rworldmap )

base_map <- getMap( resolution = "low" )
world_sf <- st_as_sf( base_map )

# Remove Penguinville
world_sf <- world_sf %>% filter( SOV_A3 != "ATA" )

# The rest of the answer uses the Winkel tripel projection.
crs_wintri <- "+proj=wintri +datum=WGS84 +no_defs +over"
world_wintri <- st_transform_proj(world_sf, crs = crs_wintri)

lats <- c(90:-90, -90:90, 90)
longs <- c(rep(c(180, -180), each = 181), 180)

wintri_outline <- 
  list(cbind(longs, lats)) %>%
  st_polygon() %>%
  st_sfc(
    crs = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"
  ) %>% 
  st_sf() %>%
  st_transform_proj(crs = crs_wintri)

# Layout the graticule and transform it to Winkel tripel.
grat_wintri <- 
  st_graticule(lat = c(-89.9, seq(-80, 80, 20), 89.9)) %>%
  st_transform_proj(crs = crs_wintri)

ggplot() +
  geom_sf(data = wintri_outline, fill = "#56B4E950", color = NA) +
  geom_sf(data = grat_wintri, color = "gray30", size = 0.25/.pt) +
  geom_sf(data = world_wintri, color = "black", size = 0.5/.pt) +
  geom_sf(data = wintri_outline, fill = NA, color = "grey30", size = 0.5/.pt) +
  coord_sf(datum = NULL) +
  theme_map()

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