Format values as dates

Format input values to time values using one of 41 preset date styles. Input can be in the form of POSIXt (i.e., datetimes), the Date type, or character (must be in the ISO 8601 form of YYYY-MM-DD HH:MM:SS or YYYY-MM-DD).

Usage

fmt_date(
  data,
  columns = everything(),
  rows = everything(),
  date_style = "iso",
  pattern = "{x}",
  locale = NULL
)

Arguments

data

The gt table data object

obj:<gt_tbl> // required

This is the gt table object that is commonly created through use of the gt() function.

columns

Columns to target

<column-targeting expression> // default: everything()

Can either be a series of column names provided in c(), a vector of column indices, or a select helper function. Examples of select helper functions include starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything().

rows

Rows to target

<row-targeting expression> // default: everything()

In conjunction with columns, we can specify which of their rows should undergo formatting. The default everything() results in all rows in columns being formatted. Alternatively, we can supply a vector of row captions within c(), a vector of row indices, or a select helper function. Examples of select helper functions include starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything(). We can also use expressions to filter down to the rows we need (e.g., [colname_1] > 100 & [colname_2] < 50).

date_style

Predefined style for dates

scalar<character>|scalar<numeric|integer>(1<=val<=41) // default: "iso"

The date style to use. By default this is the short name "iso" which corresponds to ISO 8601 date formatting. There are 41 date styles in total and their short names can be viewed using info_date_style().

pattern

Specification of the formatting pattern

scalar<character> // default: "{x}"

A formatting pattern that allows for decoration of the formatted value. The formatted value is represented by the {x} (which can be used multiple times, if needed) and all other characters will be interpreted as string literals.

locale

Locale identifier

scalar<character> // default: NULL (optional)

An optional locale identifier that can be used for formatting values according the locale's rules. Examples include "en" for English (United States) and "fr" for French (France). We can use the info_locales() function as a useful reference for all of the locales that are supported. A locale ID can be also set in the initial gt() function call (where it would be used automatically by any function with a locale argument) but a locale value provided here will override that global locale.

Value

An object of class gt_tbl.

Compatibility of formatting function with data values

The fmt_date() formatting function is compatible with body cells that are of the "Date", "POSIXt" or "character" types. Any other types of body cells are ignored during formatting. This is to say that cells of incompatible data types may be targeted, but there will be no attempt to format them.

Targeting cells with columns and rows

Targeting of values is done through columns and additionally by rows (if nothing is provided for rows then entire columns are selected). The columns argument allows us to target a subset of cells contained in the resolved columns. We say resolved because aside from declaring column names in c() (with bare column names or names in quotes) we can use tidyselect-style expressions. This can be as basic as supplying a select helper like starts_with(), or, providing a more complex incantation like

where(~ is.numeric(.x) && max(.x, na.rm = TRUE) > 1E6)

which targets numeric columns that have a maximum value greater than 1,000,000 (excluding any NAs from consideration).

By default all columns and rows are selected (with the everything() defaults). Cell values that are incompatible with a given formatting function will be skipped over, like character values and numeric fmt_*() functions. So it's safe to select all columns with a particular formatting function (only those values that can be formatted will be formatted), but, you may not want that. One strategy is to format the bulk of cell values with one formatting function and then constrain the columns for later passes with other types of formatting (the last formatting done to a cell is what you get in the final output).

Once the columns are targeted, we may also target the rows within those columns. This can be done in a variety of ways. If a stub is present, then we potentially have row identifiers. Those can be used much like column names in the columns-targeting scenario. We can use simpler tidyselect-style expressions (the select helpers should work well here) and we can use quoted row identifiers in c(). It's also possible to use row indices (e.g., c(3, 5, 6)) though these index values must correspond to the row numbers of the input data (the indices won't necessarily match those of rearranged rows if row groups are present). One more type of expression is possible, an expression that takes column values (can involve any of the available columns in the table) and returns a logical vector. This is nice if you want to base formatting on values in the column or another column, or, you'd like to use a more complex predicate expression.

Compatibility of arguments with the from_column() helper function

The from_column() helper function can be used with certain arguments of fmt_date() to obtain varying parameter values from a specified column within the table. This means that each row could be formatted a little bit differently. These arguments provide support for from_column():

• date_style

• pattern

• locale

Please note that for each of the aforementioned arguments, a from_column() call needs to reference a column that has data of the correct type (this is different for each argument). Additional columns for parameter values can be generated with the cols_add() function (if not already present). Columns that contain parameter data can also be hidden from final display with cols_hide(). Finally, there is no limitation to how many arguments the from_column() helper is applied so long as the arguments belong to this closed set.

Formatting with the date_style argument

We need to supply a preset date style to the date_style argument. The date styles are numerous and can handle localization to any supported locale. A large segment of date styles are termed flexible date formats and this means that their output will adapt to any locale provided. That feature makes the flexible date formats a better option for locales other than "en" (the default locale).

The following table provides a listing of all date styles and their output values (corresponding to an input date of 2000-02-29).

	Date Style	Output	Notes
1	"iso"	"2000-02-29"	ISO 8601
2	"wday_month_day_year"	"Tuesday, February 29, 2000"
3	"wd_m_day_year"	"Tue, Feb 29, 2000"
4	"wday_day_month_year"	"Tuesday 29 February 2000"
5	"month_day_year"	"February 29, 2000"
6	"m_day_year"	"Feb 29, 2000"
7	"day_m_year"	"29 Feb 2000"
8	"day_month_year"	"29 February 2000"
9	"day_month"	"29 February"
10	"day_m"	"29 Feb"
11	"year"	"2000"
12	"month"	"February"
13	"day"	"29"
14	"year.mn.day"	"2000/02/29"
15	"y.mn.day"	"00/02/29"
16	"year_week"	"2000-W09"
17	"year_quarter"	"2000-Q1"
18	"yMd"	"2/29/2000"	flexible
19	"yMEd"	"Tue, 2/29/2000"	flexible
20	"yMMM"	"Feb 2000"	flexible
21	"yMMMM"	"February 2000"	flexible
22	"yMMMd"	"Feb 29, 2000"	flexible
23	"yMMMEd"	"Tue, Feb 29, 2000"	flexible
24	"GyMd"	"2/29/2000 A"	flexible
25	"GyMMMd"	"Feb 29, 2000 AD"	flexible
26	"GyMMMEd"	"Tue, Feb 29, 2000 AD"	flexible
27	"yM"	"2/2000"	flexible
28	"Md"	"2/29"	flexible
29	"MEd"	"Tue, 2/29"	flexible
30	"MMMd"	"Feb 29"	flexible
31	"MMMEd"	"Tue, Feb 29"	flexible
32	"MMMMd"	"February 29"	flexible
33	"GyMMM"	"Feb 2000 AD"	flexible
34	"yQQQ"	"Q1 2000"	flexible
35	"yQQQQ"	"1st quarter 2000"	flexible
36	"Gy"	"2000 AD"	flexible
37	"y"	"2000"	flexible
38	"M"	"2"	flexible
39	"MMM"	"Feb"	flexible
40	"d"	"29"	flexible
41	"Ed"	"29 Tue"	flexible

We can use the info_date_style() function within the console to view a similar table of date styles with example output.

Adapting output to a specific locale

This formatting function can adapt outputs according to a provided locale value. Examples include "en" for English (United States) and "fr" for French (France). Note that a locale value provided here will override any global locale setting performed in gt()'s own locale argument (it is settable there as a value received by all other functions that have a locale argument). As a useful reference on which locales are supported, we can use the info_locales() function to view an info table.

Examples

Let's use the exibble dataset to create a simple, two-column gt table (keeping only the date and time columns). With the fmt_date() function, we'll format the date column to display dates formatted with the "month_day_year" date style.

exibble |>
  dplyr::select(date, time) |>
  gt() |>
  fmt_date(
    columns = date,
    date_style = "month_day_year"
  )

Again using the exibble dataset, let's format the date column to have mixed date formats, where dates after April 1st will be different than the others because of the expressions used in the rows argument. This will involve two calls of fmt_date() with different statements provided for rows. In the first call (dates after the 1st of April) the date style "m_day_year" is used; for the second call, "day_m_year" is the named date style supplied to date_style.

exibble |>
  dplyr::select(date, time) |>
  gt() |>
  fmt_date(
    columns = date,
    rows = as.Date(date) > as.Date("2015-04-01"),
    date_style = "m_day_year"
  ) |>
  fmt_date(
    columns = date,
    rows = as.Date(date) <= as.Date("2015-04-01"),
    date_style = "day_m_year"
  )

Use the exibble dataset to create a single-column gt table (with only the date column). Format the date values using the "yMMMEd" date style (which is one of the 'flexible' styles). Also, we'll set the locale to "nl" to get the dates in Dutch.

exibble |>
  dplyr::select(date) |>
  gt() |>
  fmt_date(
    date_style = "yMMMEd",
    locale = "nl"
  )

Function ID

3-13

Function Introduced

v0.2.0.5 (March 31, 2020)

See also

The vector-formatting version of this function: vec_fmt_date().

Other data formatting functions: data_color(), fmt_auto(), fmt_bins(), fmt_bytes(), fmt_currency(), fmt_datetime(), fmt_duration(), fmt_engineering(), fmt_flag(), fmt_fraction(), fmt_icon(), fmt_image(), fmt_index(), fmt_integer(), fmt_markdown(), fmt_number(), fmt_partsper(), fmt_passthrough(), fmt_percent(), fmt_roman(), fmt_scientific(), fmt_spelled_num(), fmt_time(), fmt_units(), fmt_url(), fmt(), sub_large_vals(), sub_missing(), sub_small_vals(), sub_values(), sub_zero()