mikmart/reverse-time.md

## reverse-time.md

      
    Raw
  

              reverse-time.md
            
          
    An answer to this closed StackOverflow question about reversing a time axis in ggplot2.
date = c("2011-11-15", "2011-11-16", "2011-11-17", "2011-11-19")
start = c("12:01:27", "12:01:25", "12:01:02", "12:01:12")
end = c("12:30:15", "12:32:15", "12:39:12", "12:30:18")

df = data.frame(date = as.POSIXct(date),
     ystart = as.POSIXct(start, format="%H:%M:%S"), 
     yend = as.POSIXct(end, format="%H:%M:%S"),
     xstart=as.POSIXct(paste(date, "12:00:00"), format="%Y-%m-%d %H:%M:%S"),
     xend = as.POSIXct(paste(date, "14:00:00"), format="%Y-%m-%d %H:%M:%S"))
Following this answer you can
create a custom scale transformer that applies both a time and a reverse
transformation to the y-axis to get the output that you are looking for. (It
seems a recent new release has broken the linked answer, which required a
minor modification to work again.)
library(scales)
library(ggplot2)

p <- ggplot(df) +
  geom_rect(aes(ymin = ystart, ymax = yend, xmin = xend, xmax = xstart))

c_trans <- function(a, b, breaks = b$breaks, format = b$format) {
  a <- as.trans(a)
  b <- as.trans(b)

  name <- paste(a$name, b$name, sep = "-")

  trans <- function(x) a$trans(b$trans(x))
  inv <- function(x) b$inverse(a$inverse(x))

  trans_new(name, trans, inv, breaks, format = format)
}

rev_date <- c_trans("reverse", "time")

p + scale_y_continuous(trans = rev_date)

Created on 2018-07-18 by the reprex package (v0.2.0.9000).