Plotting median for each group with ggplot facet_wrap

Question

The data set in question is diamonds(in dplyr). I am trying to break out histogram of price by cut using facet_wrap. Also I want that each plot has median line. This is how I have done -

by_cut <- group_by(diamonds, cut)

med <- by_cut %>% 
  summarise(medn = median(price))

diam <- diamonds %>% 
  mutate(med_cut = ifelse(cut == med$cut[1], med$medn[1],
                      ifelse(cut == med$cut[2], med$medn[2],
                             ifelse(cut == med$cut[3], med$medn[3],
                                    ifelse(cut == med$cut[4], med$medn[4], med$medn[5])))))

diam %>% 
  ggplot(aes(price)) +
  geom_histogram(binwidth = 100) +
  facet_wrap(~ cut, scales = "free_y") +
  geom_vline(aes(xintercept= med_cut), colour='red')

and got the required plot (as below, this is what I wanted..) -

However I am sure this is not the ideal way for achieving the outcome, Hence I would like to know what is the best way to achieve the resultant plot?

based on @yeedle comments

here is better than previous attempt:

diam <- diamonds %>% 
  group_by(cut) %>% 
  mutate(medn = median(as.numeric(price)))

diam %>% 
  ggplot(aes(price)) +
  geom_histogram(binwidth = 100) +
  facet_wrap(~ cut, scales = "free_y") +
  geom_vline(aes(xintercept= medn, group= cut), colour='red')

Can we improve it further ?

yeedle yeedle · Accepted Answer · 2017-04-04T17:54:36

diamonds %>% 
  group_by(cut) %>%
  mutate(med_price = median(as.numeric(price))) %>%
  ggplot(aes(price)) +
     geom_histogram(binwidth = 100) +
     geom_vline(aes(xintercept= med_price), colour='red') +
     facet_wrap(~ cut, scales = "free_y")

Plotting median for each group with ggplot facet_wrap

1 Answers