如何将每个方面的总样本量添加到geom_histogram？

I want to add total sample size of each facet to geom_histogram.Expect output as below:

After read this post https://stackoverflow.com/a/46289861/7936836 ,I write script as below:

iris %>% 
  ggplot(.,mapping=aes(x=Sepal.Length))+
  geom_histogram(binwidth= 0.1)+
  stat_summary(fun = median, fun.max = length,
               geom = "text", aes(label = after_stat(max)), vjust = -1) +
  facet_wrap(~Species)

但得到错误：Error: stat_summary requires the following missing aesthetics: y.
如何解决这个问题呢？

你可以试试这个：

iris %>% left_join(iris %>% group_by(Species) %>% summarise(N=n()))%>%
  mutate(Label=paste0(Species,' (Sample size = ',N,')')) %>%
  ggplot(.,mapping=aes(x=Sepal.Length))+
  geom_histogram(binwidth= 0.1)+
  facet_wrap(~Label)

它将向构面添加带有样本大小的标签：

Update

您还可以尝试：

iris %>% add_count(.,Species) %>% group_by(Species) %>% mutate(n=ifelse(row_number(n)!=1,NA,n)) %>%
  ggplot(.,mapping=aes(x=Sepal.Length))+ 
  geom_histogram(binwidth= 0.1)+ 
  facet_wrap(~Species)+ 
  geom_text(aes(label=n,y=8),size=5,vjust=-0.5)