如何将世界地图和饼图合并在一起？

Question

我有两个包含三个变量的数据集。我想在世界地图上将其中一个显示为热图，两个显示为饼图。

我使用了下面的代码，但出现了错误。我想知道如何解决它。

library(ggplot2)
library(scatterpie)

world_map <- map_data("world")
df <- data.frame(Country = c("USA", "Canada", "Mexico"),
                          Cases = c(10, 20, 30))
df_piechart <- data.frame(long = c(-95, -110, -75),
                                   lat = c(37, 60, 20),
                                   size = c(5, 10, 15),
                                   Group1 = c(20, 30, 50),
                                   Group2 = c(30, 40, 30))

ggplot() +
 geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.4 ) +
 geom_map(dat = df, map = world_map, aes(map_id = Country, fill = Cases), linewidth = 0.5) +
 scale_fill_gradient(low = "skyblue", high = "dodgerblue4", name = "Avian Cases") +
 geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.0 ) +
 expand_limits(x = world_map$long, y = world_map$lat) +
 geom_scatterpie(data = df_piechart, aes(x = long, y = lat, r = size),
                          cols = colnames(df_piechart[, c(4:5)]), alpha = 0.8) +
theme(legend.text = element_text(size = 8, family = "serif"),
    legend.title = element_text(size = 8, face = "bold", family = "serif"),
    legend.key.height = unit(0.2, 'cm'), 
    legend.key.width = unit(0.2, 'cm')) +
theme_void()

错误：

Error in `train_discrete()`:
! Continuous value supplied to a discrete scale

Answer 1

fill=（动态）在其他层美学中的使用正在被打破geom_scatterpie。2021 年， https://github.com/ericpante/marmap/issues/20#issuecomment-796591190对此进行了讨论，并指出

该错误来自于您为底图图块提供的填充调色板（此处，这是一个连续变量：对于每个深度值，都有一个关联的颜色）与用于饼图的填充颜色（在这里，这是一个离散变量：对于因子的每个级别（合法或非法），都会使用填充颜色）。

（请注意，该问题的作者将相同的问题交叉发布到多个包中，因此我链接的此评论位于不同的包中。作者在scatterpie#31scatterpie中链接到该问题。）

有两个选择：(1) 放弃您想要的fill=美观，或 (2) 添加ggnewscale::add_scale_fill()并继续使用您现有的代码。

1. fill=Cases在第二个中删除geom_map，scale_fill_gradient然后你可以绘制它（尽管可能不是你想要的）：

   gg <- ggplot() +
    geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.4 ) +
    geom_map(dat = df, map = world_map, aes(map_id = Country), linewidth = 0.5) + # , fill = Cases
    # scale_fill_gradient(low = "skyblue", high = "dodgerblue4", name = "Avian Cases") +
    geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.0 ) +
    expand_limits(x = world_map$long, y = world_map$lat) +
    geom_scatterpie(data = df_piechart, aes(x = long, y = lat, r = size),
                             cols = colnames(df_piechart[, c(4:5)]), alpha = 0.8) +
    theme(legend.text = element_text(size = 8, family = "serif"),
       legend.title = element_text(size = 8, face = "bold", family = "serif"),
       legend.key.height = unit(0.2, 'cm'), 
       legend.key.width = unit(0.2, 'cm')) +
    theme_void()
   
   gg
   

   

2. 使用ggnewscale（或其他一些允许您拥有多个色阶的包）并使用add_new_fill()，如

   gg <- ggplot() +
    geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.4 ) +
    geom_map(dat = df, map = world_map, aes(map_id = Country, fill = Cases), linewidth = 0.5) +
    scale_fill_gradient(low = "skyblue", high = "dodgerblue4", name = "Avian Cases") +
    ggnewscale::new_scale_fill() +
    geom_map(dat = world_map, map = world_map, aes(map_id = region), color = "white", fill = "#d3d4d3", linewidth = 0.5, alpha=0.0 ) +
    expand_limits(x = world_map$long, y = world_map$lat) +
    geom_scatterpie(data = df_piechart, aes(x = long, y = lat, r = size),
                             cols = colnames(df_piechart[, c(4:5)]), alpha = 0.8) +
    theme(legend.text = element_text(size = 8, family = "serif"),
       legend.title = element_text(size = 8, face = "bold", family = "serif"),
       legend.key.height = unit(0.2, 'cm'), 
       legend.key.width = unit(0.2, 'cm')) +
    theme_void()
   
   gg
   

   

旁注，您应该添加coord_quickmap()以便保留正确的比例，

gg + coord_quickmap()