Using geom_rect for time series shading in R

Question

I am trying to shade a certain section of a time series plot (a bit like recession shading - similarly to the graph at the bottom of this article on recession shading in excel). I have put a little, possibly clumsy, sample together to illustrate. I first create a time series, plot it with ggplot2 and then want to use geom_rect to provide the shading. But I must get something wrong in the arguments.

a<-rnorm(300) a_ts<-ts(a, start=c(1910, 1), frequency=12) a_time<-time(a_ts) a_series<-ts.union(big=a_ts, month=a_time) a_series_df<-as.data.frame(a_series) ggplot(a_series)+   geom_line(mapping=aes_string(x="month", y="big"))+   geom_rect(     fill="red",alpha=0.5,      mapping=aes_string(x="month", y="big"),      xmin=as.numeric(as.Date(c("1924-01-01"))),     xmax=as.numeric(as.Date(c("1928-12-31"))),     ymin=0,     ymax=2     ) 

Note that I have also tried which also did not work.

geom_rect(         fill="red",alpha=0.5,          mapping=aes_string(x="month", y="big"),          aes(            xmin=as.numeric(as.Date(c("1924-01-01"))),            xmax=as.numeric(as.Date(c("1928-12-31"))),            ymin=0,            ymax=2)         ) 

Answer 1

Its a bit easier using annotate and also note that the bounds for the rectange can be specified as shown:

ggplot(a_series_df, aes(month, big)) +      geom_line() +     annotate("rect", fill = "red", alpha = 0.5,          xmin = 1924, xmax = 1928 + 11/12,         ymin = -Inf, ymax = Inf) +     xlab("time") 

This would also work:

library(zoo)  z <- read.zoo(a_series_df, index = 2) autoplot(z) +      annotate("rect", fill = "red", alpha = 0.5,          xmin = 1924, xmax = 1928 + 11/12,         ymin = -Inf, ymax = Inf) +      xlab("time") +     ylab("big") 

Either one gives this: