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Label date/times

Source: R/label-date.R
label_date.Rd

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")

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

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

Arguments

format

For date_format() and time_format() a date/time format string using standard POSIX specification. See strptime() for details.

For 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.

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.

decimal.mark

The character to be used to indicate the numeric decimal point.

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.

style_negative

A string that determines the style of negative numbers:

  • "hyphen" (the default): preceded by a standard hypen -, 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).

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)
#> scale_x_datetime()

demo_datetime(two_months, labels = date_format("%m/%d"))
#> scale_x_datetime(labels = date_format("%m/%d"))

demo_datetime(two_months, labels = date_format("%e %b", locale = "fr"))
#> scale_x_datetime(labels = date_format("%e %b", locale = "fr"))

demo_datetime(two_months, labels = date_format("%e %B", locale = "es"))
#> scale_x_datetime(labels = date_format("%e %B", locale = "es"))

# ggplot2 provides a short-hand:
demo_datetime(two_months, date_labels = "%m/%d")
#> scale_x_datetime(date_labels = "%m/%d")


# An alternative labelling system is label_date_short()
demo_datetime(two_months, date_breaks = "7 days", labels = label_date_short())
#> scale_x_datetime(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")
#> scale_x_datetime(date_breaks = "month")

demo_datetime(one_year, date_breaks = "month", labels = label_date_short())
#> scale_x_datetime(date_breaks = "month", labels = label_date_short())