如何在ggplot2世界地图中将图例单值改为数值范围并合并标度

修改后的完整代码 #

library(ggplot2)
library(dplyr)
library(sf)
library(rnaturalearth)
library(rnaturalearthdata)

# 数据分箱处理：将连续数值转为区间因子
merged_data <- merged_data %>%
  mutate(
    yield_bin = cut(
      median_mafruit,
      breaks = c(0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0),
      labels = c("0-0.5", "0.5-1.0", "1.0-1.5", "1.5-2.0", "2.0-2.5", "2.5-3.0", "3.0-3.5", "3.5-4.0"),
      include.lowest = TRUE
    )
  )

merged_data_sf <- st_as_sf(merged_data, coords = c("longitude", "latitude"), crs = 4326)

world <- ne_countries(scale = "medium", returnclass = "sf")

colors <- c("#E31A1C", "#FF7F00", "#FDBF6F", "#E9E4A6", "#A4D4A9", "#B2DF8A", "#33A02C", "#1F78B4")
# 为每个区间设置对应尺寸，按区间从小到大递增
size_values <- seq(1, 5, length.out = length(colors))

p1 <- ggplot() +
  geom_sf(data = world, fill = "grey87", color = "white") + 
  # 映射分箱后的变量到color和size
  geom_sf(data = merged_data_sf, aes(size = yield_bin, color = yield_bin), alpha = 0.7) +
  labs(
    title = "Data1",
    subtitle = "10 years",
    x = "Longitude (°)",
    y = "Latitude (°)"
  ) +
  scale_color_manual(values = colors) +
  scale_size_manual(values = size_values) +
  coord_sf(
    xlim = c(-4.4833, 7.25),
    ylim = c(42.45, 47.21),
    expand = FALSE
  ) +
  theme_minimal() +
  theme(
    plot.title = element_text(size = 14, face = "bold"),
    plot.subtitle = element_text(size = 12, face = "italic"),
    legend.title = element_text(size = 10),
    legend.text = element_text(size = 8),
    legend.key.size = unit(0.5, "cm"),
    legend.spacing.x = unit(0.5, "cm"),
    legend.spacing.y = unit(0.5, "cm")
  ) +
  # 合并颜色和尺寸图例
  guides(
    color = guide_legend(title = bquote("Yield (t·ha"^-1*")"), order = 1),
    size = guide_legend(title = bquote("Yield (t·ha"^-1*")"), order = 1)
  )
print(p1)

关键修改说明 #

• 数据分箱：用cut()函数将连续的median_mafruit转为区间因子，直接生成数值范围标签，这是实现范围图例的核心。
• 映射调整：将aes()中的size和color统一映射到分箱后的yield_bin因子，让ggplot自动识别两个尺度的关联。
• 尺度匹配：通过scale_color_manual和scale_size_manual为每个区间指定对应的颜色和尺寸，保证视觉属性与数值范围一一对应。
• 图例合并：在guides()中给两个尺度设置相同的标题和顺序，ggplot会将它们合并为一个图例，每个条目同时展示对应颜色和尺寸。

内容的提问来源于stack exchange，提问作者Nightowl