美国人口普查部门在 ggplot2 中的映射

Question

我想按美国人口普查地区绘制数据。简而言之，我有州级数据，我使用 maps 包将其加入纬度/经度坐标。以下是生成的数据框的前 20 行：

 df_F4 %>% select(state, division, percap_rheum, group, long, lat) %>% print(n=20)
# A tibble: 15,539 x 6
# Groups:   division [9]
   state   division           percap_rheum group  long   lat
   <chr>   <chr>                     <dbl> <dbl> <dbl> <dbl>
 1 alabama east south central       70255.     1 -87.5  30.4
 2 alabama east south central       70255.     1 -87.5  30.4
 3 alabama east south central       70255.     1 -87.5  30.4
 4 alabama east south central       70255.     1 -87.5  30.3
 5 alabama east south central       70255.     1 -87.6  30.3
 6 alabama east south central       70255.     1 -87.6  30.3
 7 alabama east south central       70255.     1 -87.6  30.3
 8 alabama east south central       70255.     1 -87.6  30.3
 9 alabama east south central       70255.     1 -87.7  30.3
10 alabama east south central       70255.     1 -87.8  30.3
11 alabama east south central       70255.     1 -87.9  30.2
12 alabama east south central       70255.     1 -87.9  30.2
13 alabama east south central       70255.     1 -88.0  30.2
14 alabama east south central       70255.     1 -88.0  30.2
15 alabama east south central       70255.     1 -88.0  30.3
16 alabama east south central       70255.     1 -88.0  30.3
17 alabama east south central       70255.     1 -88.0  30.3
18 alabama east south central       70255.     1 -88.0  30.3
19 alabama east south central       70255.     1 -87.9  30.3
20 alabama east south central       70255.     1 -87.8  30.3
# … with 15,519 more rows

我想用 ggplot2 绘制它，按人口普查区域组织。我已经按地区汇总了数据，并可以在州一级绘制图表：

graph_theme <-  theme_light() + 
  theme(
    text = element_text(size=10),
    panel.grid.major.x = element_blank(), 
    panel.grid.minor = element_blank(), 
    plot.margin = unit(c(0.75, 0.25, 0.5, 0.5), "cm")) #top, R, bottom, L) 
  
map_theme <- theme(
    axis.title.x = element_blank(), 
    axis.title.y = element_blank(), 
    axis.text.x = element_blank(), 
    axis.text.y = element_blank(), 
    axis.ticks = element_blank(), 
    panel.grid = element_blank(), 
    legend.title = element_blank(), 
    legend.position = c(0.92, 0.25), # h / v 
    legend.background = element_blank()
)

df_F4 %>%
  ggplot(aes(
    long, 
    lat, 
    group = group)) +
  geom_polygon(aes(fill = percap_rheum), color = "white") + 
  scale_fill_viridis_c(labels = dollar_format(big.mark = ","), direction = -1) + 
  graph_theme + 
  map_theme

这张照片的结果是：

您可以看出那里有人口普查部门，但我想突出显示它们或以某种方式概述它们。任何建议将不胜感激！

Answer 1

一种方法是为每个分区创建一个多边形，然后将它们覆盖在状态数据上。

使用来自tigris::state() 的数据的示例。步骤是：

1. 将数据和过滤器下载到 CONUS，
2. 创建分割多边形，
3. 绘制覆盖了分区边界的状态数据。

我还更改了地理 crs，这使美国看起来有点弯曲。不过不必这样做。

library(tidyverse)
library(tigris)
library(sf)

# Download state data and filter states
sts <- states() %>%
  filter(!STUSPS %in% c('HI', 'AK', 'PR', 'GU', 'VI', 'AS', 'MP'))

# Summarize to DIVISION polygons, see sf::st_union
div <- sts %>%
  group_by(DIVISION) %>% 
  summarize()

# Plot it
ggplot() + 
  theme_void() +
  geom_sf(data = sts, 
          aes(fill = as.numeric(DIVISION)), 
          color = 'white') +
  geom_sf(data = div, 
          color = 'black', 
          fill = NA,
          size = 1) +
  scale_fill_viridis_c() +
  coord_sf(crs = 5070) +
  labs(fill = NULL)
  

---

编辑：更新为使用 maps 包。找到有用的提示here

# get data specifying which states are in which division
div_dat <- states(cb = FALSE, resolution = '20m') %>%
  st_drop_geometry() %>%
  select(NAME, DIVISION) %>%
  mutate(ID = tolower(NAME))

# get state data, convert to sf, join with division data
states <- maps::map("state", plot = FALSE, fill = TRUE) %>%
  st_as_sf() %>%
  left_join(div_dat)

# create division polygons
div <- states %>%
  group_by(DIVISION) %>% 
  summarize()

# plot it
ggplot() + 
  theme_void() +
  geom_sf(data = states, 
          aes(fill = as.numeric(DIVISION)), 
          color = 'white') +
  geom_sf(data = div, 
          color = 'black', 
          fill = NA,
          size = 1) +
  scale_fill_viridis_c() +
  coord_sf(crs = 5070) +
  labs(fill = NULL)

Answer 2

请向上面的@nniloc 寻求答案。如果有其他人跟进，我们使用 geom_sf 解决了一些问题。我尝试了一段时间让 geom_polygon 和“地图”包数据工作。这只是更高的分辨率，因为我认为有更多的数据点。

无论如何，我最终达成了妥协。不能弯曲地图，但州线本身看起来不错。简而言之，我在之前创建的地图上使用了上述划分叠加层。它看起来足够好，我想如果它可以帮助别人，我会分享。

# get data specifying which states are in which division
div_dat <- states(cb = FALSE, resolution = '20m') %>%
  st_drop_geometry() %>%
  select(NAME, DIVISION) %>%
  mutate(ID = tolower(NAME))

# get state data, convert to sf, join with division data
states <- maps::map("state", plot = FALSE, fill = TRUE) %>%
  st_as_sf() %>%
  left_join(div_dat)

# create division polygons
div <- states %>%
  group_by(DIVISION) %>% 
  summarize()

# Plot percapita spending 

ggplot() + 
  graph_theme + 
  map_theme + 
  geom_polygon(data = df_F4, 
               aes(long, lat, group = group, fill = percap_rheum), 
               color = "white") +
  geom_sf(data = div, 
          color = "#838383", 
          fill = NA,
          size = 1) + 
  scale_fill_viridis_c(labels = dollar_format(big.mark = ","), direction = -1)