Date breaks anchored to last data month (for ggplot)

Create a breaks function for scale_x_date() that always includes the last actual data month and then selects every nth month counting backward.

Usage

date_breaks_gg(n = 6, last, decreasing = FALSE)

Arguments

n

Integer; keep every n-th month counting backward from last. Default 6.

last

Date; the last (max) date in your data. Required to ensure no break is placed after your actual data.

decreasing

Logical; if TRUE, return breaks in descending order. Default FALSE.

Value

A function usable in scale_x_date(breaks = ...).

Examples

# Minimal reproducible example (avoid using the name `df`, which masks stats::df)
set.seed(1)
dat <- data.frame(
  date  = seq(as.Date("2023-01-01"), by = "month", length.out = 24),
  value = cumsum(rnorm(24))
)

library(ggplot2)

ggplot(dat, aes(date, value)) +
  geom_line() +
  scale_x_date(
    date_labels = "%b\n%Y",
    breaks = date_breaks_gg(n = 6, last = max(dat$date))
  ) +
  labs(x = NULL, y = NULL)