how to add a second x-axis to a line chart in R

Question

First is the data and the manipulations. How would I add a second y-axis to this. the desired would have 2018 under the first value (Dec), 2019 under the next 12, and then 2020 under the next 11. would this be something where I would use annotate. Furthermore, the year would be horizontal and left justified directly below the first month of the year (or dec in the case of 2018)

I have seen other questions like this but the answers have items such as xlim that is not needed being that there will be only 24 items in the dataset.

 #Data generation
 Month1 <- c(201812,20191,20192,20193,20194,20195,20196,
        20197,20198,20199,201910,201911,201912,20201
        ,20202,20203,20204,20205,20206,20207
        ,20208,20209,202010,202011)
       Rate <- 
       c(3.3,3.4,3.1,3.0,3.1,2.9,2.6,2.5,2.3,2.1,1.6,1.7,1.5,1.7,1.1,-0.4,
      -19.5,-17.6,-10.5,-9.6,-9.1,-8.6,-8.0,-7.7)
      cesyoy <- data.frame(Month1,Rate)

      #Chart
      library(ggplot2)
      library(dplyr)
      library(lubridate)
      library(scales)
      library(odbc)


     ## chart
     linechart<-cesyoy %>% mutate(year = substr(as.character(Month1),1,4),
              month = substr(as.character(Month1),5,7),
              date = as.Date(paste(year,month,"1",sep ="-"))) %>%  
     ggplot()+geom_line(aes(x=date,y=Rate),color="red")+scale_y_continuous(labels = 
     scales::percent)+scale_x_date(date_breaks="1 month", date_labels="%b\n")+theme(panel.grid.major 
     = element_blank(),axis.text.x = element_text(angle = 90, size=rel(0.6)))+ggtitle("Employment 
     Growth (%)")
     print(linechart)

Answer 1

Try this:

library(ggplot2)
library(dplyr)
library(lubridate)
library(scales)
## chart
cesyoy %>% mutate(year = substr(as.character(Month1),1,4),
                             month = substr(as.character(Month1),5,7),
                             date = as.Date(paste(year,month,"1",sep ="-"))) %>%  
  ggplot()+geom_line(aes(x=date,y=Rate),color="red")+
  scale_y_continuous(labels =scales::percent)+
  scale_x_date(date_breaks="1 month", date_labels="%b\n",
               sec.axis = dup_axis(labels = function(x) format(x,'%Y')))+
  theme(panel.grid.major= element_blank(),
  axis.text.x = element_text(angle = 90, size=rel(0.6)))+ggtitle("Employment 
     Growth (%)")

Output:

Another option:

#Code2
cesyoy %>% mutate(year = substr(as.character(Month1),1,4),
                  month = substr(as.character(Month1),5,7),
                  date = as.Date(paste(year,month,"1",sep ="-"))) %>%  
  ggplot()+geom_line(aes(x=date,y=Rate),color="red")+
  scale_y_continuous(labels =scales::percent)+
  scale_x_date(date_breaks="1 month", date_labels="%b\n",
               expand = c(0, 0))+
  facet_wrap(.~year,scales = 'free_x',strip.position = 'bottom')+
  theme(panel.grid.major= element_blank(),
        axis.text.x = element_text(angle = 90, size=rel(0.6)),
        panel.spacing = unit(0, "lines"),
        strip.placement = 'outside',
        strip.background = element_blank())+
        ggtitle("Employment 
     Growth (%)")

Output: