让你开始：您可以提取中断并应用这些中断以使其至少“半自动”：

library(ggplot2)
p1 <- ggplot(mtcars, aes(x = hp, y = mpg, color = factor(am))) 
brk <- ggplot_build(p1)$layout$panel_params[[1]]$y$breaks
brk <- brk[-c(1, length(brk))]

ggplot(mtcars, aes(x = hp, y = mpg, color = factor(am))) +
  geom_point() +
  coord_polar() +
  labs(color = 'am') +
  theme(axis.ticks.y=element_blank(),
      axis.text.y=element_blank())+
  annotate('text', x = 0, y = brk, label = as.character(brk))

创建于2022-10-31使用reprex v2.0.2

在user 12728748的答案的基础上，您还可以使用ggplot自己的scales::extended_breaks方法直接计算中断。
注意：对于极坐标，计算的间断点的限制似乎被丢弃。这似乎类似于间断点与guide_legend函数一起用于连续数据时的行为（另请参见：How does ggplot calculate its default breaks?）.我不知道这到底发生在哪里-but maybe someone knows an answer to this question.

library(ggplot2)
my_breaks <- scales::extended_breaks()(mtcars$mpg)
my_breaks <- my_breaks[2:(length(my_breaks)-1)] ## in polar coordinates, the limits of the breaks are not used

ggplot(mtcars, aes(x = hp, y = mpg, color = factor(am))) +
  geom_point() +
  coord_polar() +
  labs(color = 'am') +
  annotate('text', x = 0, y = my_breaks, label = my_breaks, size = 9*5/14) +
  theme(axis.text.y = element_blank(), 
        axis.ticks.y = element_blank())

创建于2023-04-01使用reprex v2.0.2