Annotate with ggplot2 when axis is of class 'date'

Question

I'm dealing a lot with geom_line plots these days. What is the easiest way to annotate on a plot with an axis of class date? Other than to convert the date variable to a different class?

Here's my code:

china_trades %>% 
  filter(type %in% c("Imports")) %>%
  ggplot() +
  geom_line(aes(x = month, y = dollars, group = 1)) +
  theme_minimal()

I would like to annotate the last data point which is at 2017-10 and 48.

Here's my plot:

Answer 1

Maybe somebody can chime in with a pure gg way of doing this but the directlabels package has this functionality:

china_trades %>% 
  filter(type %in% c("Imports")) %>%
  ggplot() +
  geom_line(aes(x = month, y = dollars, group = 1)) +
  theme_minimal() +
  geom_dl(aes(label = month), method = list(dl.combine("last.points")))

Edit: Here's a gg way using annotate:

x <- as.Date(c('2016-1-1','2016-1-2','2016-1-3','2016-1-4'))
y <- c(4,1,2,3)
df <- data.frame(x,y)

lastDate<- max(x)
lastDateY <- df[x==lastDate,2]

ggplot(df) +
  geom_line(aes(x = x, y = y)) +
  annotate(geom='text', x=lastDate,y=lastDateY, vjust=-2, label="China")