ggplot2：stat_summary 与 geom_boxplot 的水平位置

Question

我想使用ggplot2. 但是，我无法弄清楚如何将标记它们各自框内均值的符号水平居中（见下图）。

MWE如下供参考：

library(ggplot2)
ggplot(data=mpg, mapping=aes(x=class, y=hwy)) + 
  geom_boxplot(aes(color = drv), outlier.shape = NA) +
  stat_summary(fun.y = mean, geom = "point", size=2, aes(shape = drv, color = drv)) + 
  theme_bw()

Answer 1

试试 position_dodge()

ggplot(data=mpg, mapping=aes(x=class, y=hwy)) + 
       geom_boxplot(aes(color = drv), outlier.shape = NA) +
       stat_summary(fun.y = mean, geom = "point", size=2, aes(shape = drv, color = drv), 
                    position = position_dodge(width = .75)) + 
       theme_bw()