Creating a quarterly time interview using ggplot and lubridate

Question

I've created a time series plot using ggplot and lubridate that depicts disease incidents over a two year period. I can't seem to find a way of getting the X axis labels to depict years and quarters.

library(tidyverse)
Event.number <- c(1:30)
Event.date <- sample(seq(as.Date('2010/01/01'), as.Date('2012/12/31'), by="day"), 30)      
Disease <- c("A", "A", "B", "A", "B","A", "A", "B", "A", "B","A", "A", "B", "A", "B","A", "A", "B", "A", "B" ,"A", "A", "B", "A", "B","A", "A", "B", "A", "B")

data.frame(Event.number, Event.date, Disease) %>% 
  mutate(Year.Quarter = quarter(Event.date, with_year = TRUE)) %>% 
  select(Event.number, Year.Quarter, Disease) %>% 
  group_by(Year.Quarter, Disease) %>% 
  count(name = "Cases") %>% 
  ggplot(aes(Year.Quarter, Cases, colour = Disease))+
  geom_point()+
  geom_line()+
  theme_minimal()

Any help or advice would be greatly appreciated.

Answer 1

As per comment under the question, change the mutate as shown to use yearqtr class and add scale_x_yearqtr() to the ggplot command. Also note that the group_by/count statements can be reduced to just a count statement. See the format= argument at ?scale_x_yearqtr for further customization of the label.

library(zoo)

DF <-  data.frame(Event.number, Event.date, Disease) %>% 
  mutate(Year.Quarter = as.yearqtr(Event.date)) %>%
  select(Event.number, Year.Quarter, Disease) %>% 
  count(Year.Quarter, Disease, name = "Cases")

ggplot(DF, aes(Year.Quarter, Cases, colour = Disease)) +
    geom_point() +
    geom_line() +
    theme_minimal() +
    scale_x_yearqtr(n = 99)