Reverse Datetime (Posixct Data) Axis in Ggplot

Reverse datetime (POSIXct data) axis in ggplot version 3+

Is this what you're trying to achieve?

y-scale as time, earliest time at the bottom:

ggplot(myData, aes(y=value, x=timestamp)) +
  geom_path() +
  scale_x_datetime() + 
coord_flip()

The code posted in the question works for me. Is this the desired output:

Reverse datetime (POSIXct data) axis in ggplot

With the help from this post from Hadley Wickham here is how you can get a reverse datetime scale:

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)

Here is the plot:

How to reverse order of x-axis breaks in ggplot?

This is exactly what scale_x_reverse is for:

ggplot(test2, aes(Freq, SD, z = Intro_0)) +
  geom_contour_filled(bins = 9)+
  scale_fill_brewer(palette = "BuPu")+
  labs(x = "Frequency", y = "Magnitude", title = "Test Plot", fill = "Legend") +
  scale_x_reverse(breaks = c(1, 2, 3, 5, 10, 15, 20), 
                  labels = c("Freq = 1/1", "", "", "", "", "", "Freq = 1/20")) +
  theme_bw()+
  theme(panel.border = element_blank(), 
        panel.grid.major = element_blank(), 
        panel.grid.minor = element_blank(), 
        axis.line = element_line(colour = "white"),
        axis.text.x = element_text(angle = 45, hjust=1), 
        plot.caption.position = "plot", 
        plot.caption = element_text(hjust = 0)) 

In R, how can I extend a posixct timeseries axis beyond the end of the data

You can use the limits argument within scale_x_datetime to expand the scale.

library(dplyr)
library(ggplot2)
library(scales)
library(lubridate)

# Example data
df <- data.frame(date = as.POSIXct(
  c(
    "2016-12-05-16.25.54.875000",
    "2016-12-06-15.25.54.875000",
    "2016-12-08-14.25.54.875000",
    "2016-12-09-13.25.54.875000",
    "2016-12-09-12.25.54.875000",
    "2016-12-10-11.25.54.875000",
    "2016-12-10-10.25.54.875000",
    "2016-12-11-07.25.54.875000"
  ),
  format = "%Y-%m-%d-%H.%M.%S"
) ,
y = 1:8)

Default axis limits

The minimum and maximum values of date are the default limits, even if there is no label or tick mark at the spot.

ggplot(df, aes(x = date, y = y)) +
  geom_point() +
  scale_x_datetime(labels = date_format("%D"),
                   date_breaks = "2 day")

Expanded axis limits

We can expand the axis limits even to values not observed in our data. Once again, you'll need to adjust labels and tick marks if you want to scale them the same as well.

ggplot(df, aes(x = date, y = y)) +
  geom_point() +
  scale_x_datetime(
    labels = date_format("%D"),
    date_breaks = "2 day",
    limits = ymd_h("2016-12-05 00", "2016-12-20 23")
  )

Reversing the y axis on discrete data

Use:

ylim("20220427", "20220420", "20220413") 

Reverse x-axis that contains categorical data and a lot of annotations

We could make annotation labels and shading part of the input data. Then annotations will reverse together with x-axis ordering. Something like:

library(tidyverse)

# dummy data
mtcars %>%
  mutate(make =  word(rownames(mtcars))) %>%
  group_by(make) %>%
  summarize(wt = sum(wt)) %>%
  head ->
  mt

# Option to reverse, choose one
# if it is a function, pass an argument
# foo <- function(data, myReverseOption = FALSE, ...
myReverseOption = TRUE
myReverseOption = FALSE

mt$make <- as.factor(mt$make)

if(myReverseOption){
  mt$make <- factor(mt$make, levels = rev(levels(mt$make))) }

# add annotaions
mt <- mt %>% 
  mutate(
    myLabel = if_else(make == "Camaro", "OK, y'all?", NA_character_),
    myShade = grepl("^C", make))

# plot
ggplot(mt, aes(x = make, y = wt)) +
  geom_bar(stat = "identity") +
  geom_text(aes(label = myLabel), nudge_y = 1) +
  geom_rect(aes(xmin = (as.numeric(make) - 0.5) * myShade,
                xmax = (as.numeric(make) + 0.5) * myShade,
                ymin = 4, ymax = 6),
            alpha = 0.5) +
  ggtitle(ifelse(myReverseOption, "reversed", "original"))

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