ggplot - 在地图顶部创建边框覆盖

Question

因此，我正在尝试根据自定义变量创建带有边界的佛罗里达县级地图。我在这里添加了我正在尝试创建的旧版地图

从本质上讲，该地图显示了佛罗里达州县的区域细分，媒体市场用黑粗线边框勾勒出来。我能够很容易地绘制这些区域。我希望添加的是在媒体市场变量“MMarket”定义的区域之外的更粗的黑线边框，类似于上面显示的地图。填充变量将是 Region，媒体市场边界轮廓将使用 MMarket 定义。以下是数据的读取和强化方式：

#read in data
fl_data <- read_csv("Data for Mapping.csv")

#read in shapefiles
flcounties1 <- readOGR(dsn =".",layer = "Florida Counties")

#Fortify based on county name
counties.points <- fortify(flcounties1, region = "NAME")
counties.points$id <- toupper(counties.points$id)

#Merge plotting data and geospatial dataframe 
merged <- merge(counties.points, merged_data, by.x="id", by.y="County", all.x=TRUE)

fl_data 对象包含要映射的数据（包括媒体市场变量），并将 shapefile 数据读入flcounties1。这是我正在使用的合并数据框的示例：

 head(merged %>% select(id:group, Region, MMarket))
       id      long      lat order  hole piece     group    Region     MMarket
1 ALACHUA -82.65855 29.83014     1 FALSE     1 Alachua.1 Panhandle Gainesville
2 ALACHUA -82.65551 29.82969     2 FALSE     1 Alachua.1 Panhandle Gainesville
3 ALACHUA -82.65456 29.82905     3 FALSE     1 Alachua.1 Panhandle Gainesville
4 ALACHUA -82.65367 29.82694     4 FALSE     1 Alachua.1 Panhandle Gainesville
5 ALACHUA -82.65211 29.82563     5 FALSE     1 Alachua.1 Panhandle Gainesville
6 ALACHUA -82.64915 29.82648     6 FALSE     1 Alachua.1 Panhandle Gainesville

我可以使用以下代码轻松获得区域变量的地图：

ggplot() +
  # county polygons
  geom_polygon(data = merged, aes(fill = Region,
                                  x = long,
                                  y = lat,
                                  group = group)) +
  # county outline
  geom_path(data = merged, aes(x = long, y = lat, group = group), 
            color = "black", size = 1) +
  coord_equal() +
  # add the previously defined basic theme
  theme_map() +
  labs(x = NULL, y = NULL, 
       title = "Florida: Regions by County") +
  scale_fill_brewer(palette = "Set3",
                    direction = 1,
                    drop = FALSE,
                    guide = guide_legend(direction = "vertical",
                                         title.hjust = 0,
                                         title.vjust = 1,
                                         barheight = 30,
                                         label.position = "right",
                                         reverse = T,
                                         label.hjust = 0))

Answer 1

如果您想使用ggplot2::geom_sf 进入sf，这是一个简单的示例。由于我没有你的 shapefile，我只是使用tigris 下载康涅狄格州的县分区 shapefile，然后将其转换为简单的要素对象。

更新说明：随着sf 的更新版本，一些事情似乎发生了变化，因此您现在应该只使用summarise 将城镇合并为县。

# download the shapefile I'll work with
library(dplyr)
library(ggplot2)
library(sf)

ct_sf <- tigris::county_subdivisions(state = "09", cb = T, class = "sf")

如果我想按原样绘制这些城镇，我可以使用ggplot 和geom_sf：

ggplot(ct_sf) +
  geom_sf(fill = "gray95", color = "gray50", size = 0.5) +
  # these 2 lines just clean up appearance
  theme_void() +
  coord_sf(ndiscr = F)

在没有任何功能的情况下分组和调用summarise 可为您提供多种功能的结合。我将根据县级 FIPS 代码（COUNTYFP 列）联合城镇。 sf 函数适合 dplyr 管道，太棒了。

所以这个：

ct_sf %>% 
    group_by(COUNTYFP) %>% 
    summarise()

会给我一个sf 对象，其中所有城镇都已合并到他们的县中。我可以将这两者结合起来，在第一层 geom_sf 中获得城镇地图，并在第二层中动态地对县进行联合：

ggplot(ct_sf) +
  geom_sf(fill = "gray95", color = "gray50", size = 0.5) +
  geom_sf(fill = "transparent", color = "gray20", size = 1, 
          data = . %>% group_by(COUNTYFP) %>% summarise()) +
  theme_void() +
  coord_sf(ndiscr = F)

没有更多fortify！

Answer 2

可能有更好的方法，但我的解决方法是在您需要绘制的所有维度中强化数据。

在你的情况下，我将创建你的县和 MMarkets 的强化数据集并像你一样绘制地图，但添加一层 geom_polygon 没有填充，所以只绘制边界。

merged_counties   <- fortify(merged, region = "id")
merged_MMarket    <- fortify(merged, region = "MMarket")

然后

ggplot() +
  # county polygons
  geom_polygon(data = merged_counties, aes(fill = Region,
                                  x = long,
                                  y = lat,
                                  group = group)) +
# here comes the difference
geom_polygon(data = merged_MMarket, aes(x = long,
                                  y = lat,
                                  group = group),
                                  fill = NA, size = 0.2) +
  # county outline
  geom_path(data = merged, aes(x = long, y = lat, group = group), 
            color = "black", size = 1) +
  coord_equal() +
  # add the previously defined basic theme
  theme_map() +
  labs(x = NULL, y = NULL, 
       title = "Florida: Regions by County") +
  scale_fill_brewer(palette = "Set3",
                    direction = 1,
                    drop = FALSE,
                    guide = guide_legend(direction = "vertical",
                                         title.hjust = 0,
                                         title.vjust = 1,
                                         barheight = 30,
                                         label.position = "right",
                                         reverse = T,
                                         label.hjust = 0))

使用巴西形状文件的示例

brasil      <- readOGR(dsn = "path to shape file", layer = "the file")
brasilUF    <- fortify(brasil, region = "ID_UF")
brasilRG    <- fortify(brasil, region = "REGIAO")

ggplot() +
  geom_polygon(data = brasilUF, aes(x = long, y = lat, group = group), fill = NA, color = 'black')  +
  geom_polygon(data = brasilRG, aes(x = long, y = lat, group = group), fill = NA, color = 'black', size = 2) +
  theme(rect            = element_blank(), # drop everything and keep only maps and legend
        line            = element_blank(),
        axis.text.x     = element_blank(),
        axis.text.y     = element_blank(),
        axis.title.x    = element_blank()
  ) +
  labs(x = NULL, y = NULL) +
  coord_map()