fmt_flag: Generate flag icons for countries from their country codes

View source: R/format_data.R

fmt_flagR Documentation

Generate flag icons for countries from their country codes


While it is fairly straightforward to insert images into body cells (using fmt_image() is one way to it), there is often the need to incorporate specialized types of graphics within a table. One such group of graphics involves iconography representing different countries, and the fmt_flag() function helps with inserting a flag icon (or multiple) in body cells. To make this work seamlessly, the input cells need to contain some reference to a country, and this is in the form of a 2-letter ISO 3166-1 country code (e.g., Egypt has the "EG" country code). This function will parse the targeted body cells for those codes (and the countrypops dataset contains all of them) and insert the appropriate flag graphics. Multiple flags can be included per cell by separating country codes with commas (e.g., "GB,TT"). The sep argument allows for a common separator to be applied between flag icons.


  columns = everything(),
  rows = everything(),
  height = "1em",
  sep = " ",
  use_title = TRUE



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 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 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).


Height of flag

⁠scalar<character>⁠ // default: "1em"

The absolute height of the flag icon in the table cell. By default, this is set to "1em".


Separator between flags

⁠scalar<character>⁠ // default: " "

In the output of flag icons within a body cell, sep provides the separator between each icon. By default, this is a single space character (" ").


Display country name on hover

⁠scalar<logical>⁠ // default: TRUE

An option to display a tooltip for the country name (in English) when hovering over the flag icon.


An object of class gt_tbl.

Compatibility of formatting function with data values

The fmt_flag() formatting function is compatible with body cells that are of the "character" or "factor" 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_flag() 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():

  • height

  • sep

  • use_title

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.

Flag icons that can be used

You can view the entire set of supported flag icons as an informative table by using the info_flags() function. In the information table that is provided, you'll see every flag icon and the associated identifier that can be used with fmt_flag().


Use the countrypops dataset to create a gt table. We will only include a few columns and rows from that table. The country_code_2 column has 2-letter country codes in the format required for fmt_flag() and using that function transforms the codes in circular flag icons.

countrypops |>
  dplyr::filter(year == 2021) |>
  dplyr::filter(grepl("^S", country_name)) |>
  dplyr::arrange(country_name) |>
  dplyr::select(-country_code_3, -year) |>
  dplyr::slice_head(n = 10) |>
  gt() |>
  cols_move_to_start(columns = country_code_2) |>
  fmt_integer() |>
  fmt_flag(columns = country_code_2) |>
    country_code_2 = "",
    country_name = "Country",
    population = "Population (2021)"
This image of a table was generated from the first code example in the `fmt_flag()` help file.

Using countrypops we can generate a table that provides populations every five years for the Benelux countries ("BE", "NL", and "LU"). This requires some manipulation with dplyr and tidyr before introducing the table to gt. With fmt_flag() we can obtain flag icons in the country_code_2 column. After that, we can merge the flag icons into the stub column, generating row labels that have a combination of icon and text.

countrypops |>
  dplyr::filter(country_code_2 %in% c("BE", "NL", "LU")) |>
  dplyr::filter(year %% 10 == 0) |>
  dplyr::select(country_name, country_code_2, year, population) |>
  tidyr::pivot_wider(names_from = year, values_from = population) |>
  dplyr::slice(1, 3, 2) |>
  gt(rowname_col = "country_name") |>
  tab_header(title = "Populations of the Benelux Countries") |>
  tab_spanner(columns = everything(), label = "Year") |>
  fmt_integer() |>
  fmt_flag(columns = country_code_2) |>
    columns = c(country_name, country_code_2),
    pattern = "{2} {1}"
This image of a table was generated from the second code example in the `fmt_flag()` help file.

The fmt_flag() function works well even when there are multiple country codes within the same cell. It can operate on comma-separated codes without issue. When rendered to HTML, hovering over each of the flag icons results in tooltip text showing the name of the country.

countrypops |>
  dplyr::filter(year == 2021, population < 100000) |>
  dplyr::select(country_code_2, population) |>
  dplyr::mutate(population_class = cut(
    breaks = scales::breaks_pretty(n = 5)(population)
  ) |>
  dplyr::group_by(population_class) |>
    countries = paste0(country_code_2, collapse = ",")
  ) |>
  dplyr::arrange(desc(population_class)) |>
  gt() |>
  tab_header(title = "Countries with Small Populations") |>
  fmt_flag(columns = countries) |>
    columns = population_class,
    fmt = ~ fmt_integer(., suffixing = TRUE)
  ) |>
    population_class = "Population Range",
    countries = "Countries"
  ) |>
  cols_width(population_class ~ px(150))
This image of a table was generated from the third code example in the `fmt_flag()` help file.

Function ID


Function Introduced

v0.9.0 (Mar 31, 2023)

See Also

Other data formatting functions: data_color(), fmt_auto(), fmt_bins(), fmt_bytes(), fmt_currency(), fmt_datetime(), fmt_date(), fmt_duration(), fmt_engineering(), 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()

gt documentation built on June 22, 2024, 11:11 a.m.