如何将Inset Plot的图例单独置于整张图表底部？

要实现这个需求，核心思路是先隐藏内嵌图自带的图例，提取图例后再将主图（含内嵌图）和图例垂直组合，具体步骤及修改后的代码如下：

步骤1：修正内嵌图的图例设置 #

首先修改你的inset绘图代码，把错误的legend.location参数改为legend.position = "none"，让内嵌图本身不显示图例：

inset <- ggplot() +
  geom_sf(data = dat.eez.usa1, size = 1.5, aes(color = "eez"), fill = 'transparent')+
  scale_color_manual(name = "", 
                     values = c(eez = "lightblue"), 
                     labels = c('EEZ')) +
  coord_sf(xlim = c(-117, -121.5), ylim = c(31.75, 36), expand = FALSE)+
  scale_x_continuous(breaks = c(seq(from = -121, to = -117, by = 2))) +
  scale_y_continuous(breaks = c(seq(from = 32, to = 36, by = 2)))+
  theme(
        strip.background = element_blank(), 
        strip.text.x = element_text(
          size = 12, hjust = 0, face = "bold"),
        panel.border = element_rect(color = "red", 
                                    fill = NA, 
                                    linewidth = 1),
        axis.line.y = element_blank(), axis.line.x = element_blank(),
        axis.title.x=element_blank(),
        axis.title.y=element_blank(),
        axis.text.x = element_text(size = 6),
        axis.text.y = element_text(size = 6),
        legend.position = "none")  # 隐藏内嵌图自带的图例

步骤2：提取内嵌图的图例 #

使用ggpubr包的get_legend()函数提取图例（未安装的话先运行install.packages("ggpubr")）：

library(ggpubr)
inset_legend <- get_legend(
  # 生成临时带图例的图表，用于提取样式匹配的图例
  ggplot() +
    geom_sf(data = dat.eez.usa1, size = 1.5, aes(color = "eez"), fill = 'transparent')+
    scale_color_manual(name = "", 
                       values = c(eez = "lightblue"), 
                       labels = c('EEZ')) +
    theme(legend.position = "bottom")  # 设置图例横向显示
)

步骤3：组合主图（含内嵌图）与图例 #

用patchwork包（未安装先运行install.packages("patchwork")）将带内嵌图的主图和提取的图例垂直拼接，调整高度比例让布局更协调：

library(patchwork)
# 创建带内嵌图的主图对象
main_with_inset <- ggdraw(bigger_plot) +
  draw_plot(inset,
            x = .086, 
            y = 0.15,
            width = 0.45, 
            height = 0.45)

# 垂直组合布局：主图在上，图例在下
final_plot <- main_with_inset / inset_legend +
  plot_layout(heights = c(10, 1))  # 调整主图与图例的高度占比

# 查看最终图表
print(final_plot)

完整修改后的代码 #

# 安装依赖包（如果未安装）
# install.packages(c("ggpubr", "patchwork", "sf", "rnaturalearth", "ggplot2", "ggdraw", "maps"))

library(sf)
library(rnaturalearth)
library(ggplot2)
library(ggdraw)
library(ggpubr)
library(patchwork)
library(maps)

path.eez.usa <- ("~/Downloads/EEZ_land_union_v3_202003/")
fnam.eez.usa <- "EEZ_Land_v3_202030.shp"
eez.usa <- st_read(dsn = path.eez.usa, layer = file_path_sans_ext(fnam.eez.usa))

dat.eez.usa1 <- fortify(eez.usa) 
world <- ne_countries(scale = "medium", returnclass = "sf")

bigger_plot <- ggplot()+
  geom_sf(data = world)+
  borders("state") +
  scale_x_continuous(breaks = c(seq(from = -140, to = -114, by = 5))) +
  scale_y_continuous(breaks = c(seq(from = 29, to = 50, by = 2))) +
  coord_sf(xlim = c(-113, -140), ylim = c(29, 50.5), expand = FALSE)+
  theme(strip.background = element_blank(), 
        legend.position = 'bottom', 
        strip.text.x = element_text(
          size = 12, hjust = 0, face = "bold"),
        axis.title.x=element_blank(),
        axis.title.y=element_blank())

# 修改内嵌图，隐藏自带图例
inset <- ggplot() +
  geom_sf(data = dat.eez.usa1, size = 1.5, aes(color = "eez"), fill = 'transparent')+
  scale_color_manual(name = "", 
                     values = c(eez = "lightblue"), 
                     labels = c('EEZ')) +
  coord_sf(xlim = c(-117, -121.5), ylim = c(31.75, 36), expand = FALSE)+
  scale_x_continuous(breaks = c(seq(from = -121, to = -117, by = 2))) +
  scale_y_continuous(breaks = c(seq(from = 32, to = 36, by = 2)))+
  theme(
        strip.background = element_blank(), 
        strip.text.x = element_text(
          size = 12, hjust = 0, face = "bold"),
        panel.border = element_rect(color = "red", 
                                    fill = NA, 
                                    linewidth = 1),
        axis.line.y = element_blank(), axis.line.x = element_blank(),
        axis.title.x=element_blank(),
        axis.title.y=element_blank(),
        axis.text.x = element_text(size = 6),
        axis.text.y = element_text(size = 6),
        legend.position = "none")

# 提取内嵌图的图例
inset_legend <- get_legend(
  ggplot() +
    geom_sf(data = dat.eez.usa1, size = 1.5, aes(color = "eez"), fill = 'transparent')+
    scale_color_manual(name = "", 
                       values = c(eez = "lightblue"), 
                       labels = c('EEZ')) +
    theme(legend.position = "bottom")
)

# 组合主图（含内嵌图）和图例
main_with_inset <- ggdraw(bigger_plot) +
  draw_plot(inset,
            x = .086, 
            y = 0.15,
            width = 0.45, 
            height = 0.45)

final_plot <- main_with_inset / inset_legend +
  plot_layout(heights = c(10, 1))

print(final_plot)

关键说明 #

• 原代码中legend.location是错误参数，正确控制图例位置的参数是legend.position。
• 提取图例时需生成临时图表，确保图例的样式、颜色与内嵌图完全匹配。
• 通过patchwork的/运算符实现垂直布局，plot_layout(heights)可灵活调整主图与图例的高度占比，优化视觉效果。

内容的提问来源于stack exchange，提问作者awray