Reverse datetime (POSIXct data) axis in ggplot previous solution broken

Question

A previous post detailed a solution to reversing the time on a ggplot post with this data:

MyData <-
  structure(list(Date = structure(c(1492979809.99827, 1492602845.68722, 
  1493093428.90318, 1492605578.0691, 1492961342.65056, 1492771976.83545, 
  1493020588.88485, 1493057018.85104, 1492852011.23873, 1492855996.55059
  ), class = c("POSIXct", "POSIXt")), Value = c(4.52885504579172, 
  6.0024610790424, 8.96430060034618, 7.06435370026156, 5.08460514713079, 
  3.47828012891114, 6.29844291834161, 0.898315710946918, 1.44857675535604, 
  5.74641009094194)), .Names = c("Date", "Value"), row.names = c(NA, 
  -10L), class = "data.frame")

and this solution:

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, inverse = inv, breaks = breaks, format=format)

}

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

ggplot(MyData, aes(x=Value, y=Date)) +
  geom_point() + 
  scale_y_continuous(trans = rev_date)

However, when I try and run this code now I get the following error: Error: Invalid input: time_trans works with objects of class POSIXct only

I am running this code on R version 4.2.2 and cannot find a solution to fix this.

I tried forcing my data into POSIXct format, but the graphing still breaks in the same way.

Your example does not seem to cause an error on my laptop (R 4.1.1). Have you remembered `library(scales)`? — Oliver, Nov 14 '22 at 15:14
Yes, I currently have library(scales) and library(ggplot2). I am worried that this might be a version issue. — Kieran Liming, Nov 14 '22 at 15:43

score 1 · Accepted Answer · answered Nov 14 '22 at 18:05

You could slightly modify the function coord_x_datetime from the tidyquant package to reverse the datetime for your y-axis. Here is the function called coord_y_datetime:

coord_y_datetime <- function(xlim = NULL, ylim = NULL, expand = TRUE) {
  if (!is.null(ylim)) {
    ylim <- lubridate::as_datetime(ylim)
  }
  ggplot2::coord_cartesian(xlim = xlim, ylim = ylim, expand = expand)
}

Here is a reproducible example:

library(ggplot2)
ggplot(MyData, aes(x = Value, y = Date)) +
  geom_point() + 
  coord_y_datetime(ylim = c(max(MyData$Date), min(MyData$Date)))

^{Created on 2022-11-14 with reprex v2.0.2}

Reverse datetime (POSIXct data) axis in ggplot previous solution broken

1 Answers1