Ggplot2: No secondary axis for date/datetime scales?

ggplot2

#1

I’ve just noticed that sec.axis does not appear to be supported for date or datetime scales in ggplot2.

Is this a deliberate decision or an oversight?

I tend to add a duplicate y-axis where there are many data points, particularly where the x-axis is date-based as the most recent data will be on the right of the plot.

Example:

library(tidyverse)
library(lubridate)

dummy_data <- 
  tribble(~id, ~start, ~finish, 
          1L, "2017-12-11 09:00:00", "2017-12-11 17:00:00", 
          2L, "2017-12-12 09:13:00", "2017-12-12 16:58:00", 
          3L, "2017-12-13 08:51:00", "2017-12-13 17:12:00", 
          4L, "2017-12-14 09:15:00", "2017-12-14 16:49:00", 
          5L, "2017-12-15 09:22:00", "2017-12-14 17:03:00") %>% 
  mutate(start_date = as_date(start), 
         finish_date = as_date(finish), 
         start = strftime(start, format = "%H:%M:%S", tz = "UTC"), 
         finish = strftime(finish, format = "%H:%M:%S", tz = "UTC")) %>% 
  filter(start_date == finish_date) %>% 
  gather(start_finish, dummy_time, start, finish) %>% 
  mutate(dummy_time = ymd_hms(paste("2017-12-11", dummy_time)))

p <- 
  ggplot(dummy_data, 
         aes(x = start_date, y = dummy_time, 
             colour = start_finish)) +
  geom_line() + 
  geom_point()

# this does not work
p + scale_y_datetime(sec.axis = dup_axis())

#2

Sorry, I think I have found the answer myself:

As an alternative question: is the status likely to be reviewed in 2018?