ggplot - 在地图顶部创建边框叠加层

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。我在此处包含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各县的区域细分，媒体市场用粗体黑线边框勾勒。我能够很容易地绘制区域。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。填充变量将为 Region，媒体市场边界轮廓将使用 MMarket 定义。以下是读取和强化数据的方式：

#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)

该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很容易地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

下面是如果你想进入一个简单的例子sf用ggplot2::geom_sf。由于我没有您的 shapefile，我只是使用 下载康涅狄格州的县细分 shapefile tigris，然后将其转换为简单的要素对象。

更新说明：一些事情似乎在 的更新版本中发生了变化sf，因此您现在应该将城镇合并为县summarise。

# 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)

summarise没有功能的分组和调用为您提供了多个功能的结合。我将根据他们的县 FIPS 代码来联合城镇，这是COUNTYFP列。sf函数适合dplyr管道，这很棒。

所以这：

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

会给我一个sf所有城镇都合并到他们县的对象。我可以将这两者结合起来得到第一geom_sf层中的城镇地图，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)

没有了fortify！

Answer 2

可能有更好的方法来做到这一点，但我的解决方法是在您需要绘制的所有维度上强化数据。

在您的情况下，我将创建您的县和 MMarkets 的强化数据集，并像您一样绘制地图，但再添加一层geom_polygon不填充的图层，以便仅绘制边框。

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

进而

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()