如何使用ggdensity叠加总密度图与分组密度图

你直接用+连接两个ggdensity()会生成两张独立的图，因为每个ggdensity()都是完整的ggplot对象。要把总密度和分组密度叠加在同一图里，有两种简单的实现方式：

方法一：基于ggpubr快速实现 #

利用ggdensity先画出分组密度图，再手动添加总密度和总均值的图层：

library(ggpubr)

ggdensity(iris, x = "Sepal.Length", add = "mean", rug = TRUE,
          color = "Species", fill = "Species", alpha = 0.3) +
  # 添加总数据集的密度曲线
  geom_density(data = iris, aes(x = Sepal.Length), color = "black", size = 1) +
  # 添加总数据的均值线
  geom_vline(data = iris, aes(xintercept = mean(Sepal.Length)), 
             color = "black", linetype = "dashed", size = 1)

设置alpha=0.3是为了让分组密度的填充色半透明，不会遮挡总密度曲线。

方法二：用原生ggplot2自定义（更灵活） #

如果需要更精细控制图中元素的样式，直接用ggplot2的基础图层组合：

library(ggplot2)

ggplot() +
  # 绘制分组密度图，设置半透明填充
  geom_density(data = iris, aes(x = Sepal.Length, color = Species, fill = Species), 
               alpha = 0.3) +
  # 绘制总密度曲线（黑色粗线）
  geom_density(data = iris, aes(x = Sepal.Length), color = "black", size = 1) +
  # 添加分组的均值虚线
  stat_summary(data = iris, aes(x = Sepal.Length, color = Species), 
               fun = mean, geom = "vline", linetype = "dashed") +
  # 添加总数据的均值实线
  geom_vline(xintercept = mean(iris$Sepal.Length), color = "black", 
             linetype = "solid", size = 1) +
  # 添加rug图
  geom_rug(data = iris, aes(x = Sepal.Length, color = Species)) +
  # 可选：设置简洁主题
  theme_bw()

内容的提问来源于stack exchange，提问作者DaveR7