我想在 ggplot 图的每个方面显示一个垂直条，其中包含该方面数据的平均值。我可以针对单个方面执行此操作：
# For Petal Length Only :
Mean <- colMeans(iris["Petal.Length"])
iris %>% pivot_longer(cols = !Species,names_to = "Characteristic",values_to = "Value") %>%
filter(Characteristic=="Petal.Length") %>%
ggplot(aes(x=Value,fill=Species))+geom_density()+facet_wrap(~Characteristic)+
geom_vline(xintercept = Mean)
但是当使用小平面时，会显示 4 条垂直线，而不是每个小平面显示一条：
# For all characteristics :
Mean <- colMeans(iris[-5])
iris %>% pivot_longer(cols = !Species,names_to = "Characteristic",values_to = "Value") %>%
ggplot(aes(x=Value,fill=Species))+geom_density()+facet_wrap(~Characteristic)+geom_vline(xintercept = Mean)
# Display vertical lines for all means where I would like only one vertical bar
# by group displayed (one for petal length, one for sepal width, etc) …