label_date: Label date/times

In r-lib/scales: Scale Functions for Visualization

Label date/times

Description

label_date() and label_time() label date/times using date/time format strings. label_date_short() automatically constructs a short format string sufficient to uniquely identify labels. It's inspired by matplotlib's ConciseDateFormatter, but uses a slightly different approach: ConciseDateFormatter formats "firsts" (e.g. first day of month, first day of day) specially; date_short() formats changes (e.g. new month, new year) specially. label_timespan() is intended to show time passed and adds common time units suffix to the input (ns, us, ms, s, m, h, d, w).

Usage

label_date(format = "%Y-%m-%d", tz = "UTC", locale = NULL)

label_date_short(
  format = c("%Y", "%b", "%d", "%H:%M"),
  sep = "\n",
  leading = "0",
  tz = "UTC",
  locale = NULL
)

label_time(format = "%H:%M:%S", tz = "UTC", locale = NULL)

label_timespan(
  unit = c("secs", "mins", "hours", "days", "weeks"),
  space = FALSE,
  ...
)

Arguments

format	For label_date() and label_time() a date/time format string using standard POSIX specification. See strptime() for details. For label_date_short() a character vector of length 4 giving the format components to use for year, month, day, and hour respectively.
tz	a time zone name, see timezones(). Defaults to UTC
locale	Locale to use when for day and month names. The default uses the current locale. Setting this argument requires stringi, and you can see a complete list of supported locales with stringi::stri_locale_list().
sep	Separator to use when combining date formats into a single string.
leading	A string to replace leading zeroes with. Can be "" to disable leading characters or "\u2007" for figure-spaces.
unit	The unit used to interpret numeric input
space	Add a space before the time unit?
...	Arguments passed on to number accuracy A number to round to. Use (e.g.) 0.01 to show 2 decimal places of precision. If NULL, the default, uses a heuristic that should ensure breaks have the minimum number of digits needed to show the difference between adjacent values. Applied to rescaled data. scale A scaling factor: x will be multiplied by scale before formatting. This is useful if the underlying data is very small or very large. prefix Additional text to display before the number. The suffix is applied to absolute value before style_positive and style_negative are processed so that prefix = "$" will yield (e.g.) ⁠-$1⁠ and ⁠($1)⁠. suffix Additional text to display after the number. big.mark Character used between every 3 digits to separate thousands. The default (NULL) retrieves the setting from the number options. decimal.mark The character to be used to indicate the numeric decimal point. The default (NULL) retrieves the setting from the number options. style_positive A string that determines the style of positive numbers: "none" (the default): no change, e.g. 1. "plus": preceded by +, e.g. +1. "space": preceded by a Unicode "figure space", i.e., a space equally as wide as a number or +. Compared to "none", adding a figure space can ensure numbers remain properly aligned when they are left- or right-justified. The default (NULL) retrieves the setting from the number options. style_negative A string that determines the style of negative numbers: "hyphen" (the default): preceded by a standard hyphen -, e.g. -1. "minus", uses a proper Unicode minus symbol. This is a typographical nicety that ensures - aligns with the horizontal bar of the the horizontal bar of +. "parens", wrapped in parentheses, e.g. (1). The default (NULL) retrieves the setting from the number options. trim Logical, if FALSE, values are right-justified to a common width (see base::format()).

Value

All label_() functions return a "labelling" function, i.e. a function that takes a vector x and returns a character vector of length(x) giving a label for each input value.

Labelling functions are designed to be used with the labels argument of ggplot2 scales. The examples demonstrate their use with x scales, but they work similarly for all scales, including those that generate legends rather than axes.

Examples

date_range <- function(start, days) {
  start <- as.POSIXct(start)
  c(start, start + days * 24 * 60 * 60)
}

two_months <- date_range("2020-05-01", 60)
demo_datetime(two_months)
demo_datetime(two_months, labels = label_date("%m/%d"))
demo_datetime(two_months, labels = label_date("%e %b", locale = "fr"))
demo_datetime(two_months, labels = label_date("%e %B", locale = "es"))
# ggplot2 provides a short-hand:
demo_datetime(two_months, date_labels = "%m/%d")

# An alternative labelling system is label_date_short()
demo_datetime(two_months, date_breaks = "7 days", labels = label_date_short())
# This is particularly effective for dense labels
one_year <- date_range("2020-05-01", 365)
demo_datetime(one_year, date_breaks = "month")
demo_datetime(one_year, date_breaks = "month", labels = label_date_short())

r-lib/scales documentation built on June 14, 2025, 10:56 p.m.