R: Format URLs to generate links

fmt_url {gt}

R Documentation

Format URLs to generate links

Description

Should cells contain URLs, fmt_url() can be used to make them navigable links. This should be expressly used on columns that contain only URL text (i.e., no URLs as part of a larger block of text). Should you have such a column of data, there are options for how the links should be styled. They can be of the conventional style (with underlines and text coloring that sets it apart from other text), or, they can appear to be button-like (with a surrounding box that can be filled with a color of your choosing).

URLs in data cells are detected in two ways. The first is using the simple Markdown notation for URLs of the form: ⁠[label](URL)⁠. The second assumes that the text is the URL. In the latter case the URL is also used as the label but there is the option to use the label argument to modify that text.

Usage

fmt_url(
  data,
  columns = everything(),
  rows = everything(),
  label = NULL,
  as_button = FALSE,
  color = "auto",
  show_underline = "auto",
  button_fill = "auto",
  button_width = "auto",
  button_outline = "auto",
  target = NULL,
  rel = NULL,
  referrerpolicy = NULL,
  hreflang = 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 (e.g. `starts_with()`, `ends_with()`, `contains()`, `matches()`, `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 (e.g. `starts_with()`, `ends_with()`, `contains()`, `matches()`, `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`).
`label`	Link label `⁠scalar<character>⁠` // default: `NULL` (`optional`) The visible 'label' to use for the link. If `NULL` (the default) the URL will serve as the label. There are two non-`NULL` options: (1) a piece of static text can be used for the label by providing a string, and (2) a function can be provided to fashion a label from every URL.
`as_button`	Style link as a button `⁠scalar<logical>⁠` // default: `FALSE` An option to style the link as a button. By default, this is `FALSE`. If this option is chosen then the `button_fill` argument becomes usable.
`color`	Link color `⁠scalar<character>⁠` // default: `"auto"` The color used for the resulting link and its underline. This is `"auto"` by default; this allows gt to choose an appropriate color based on various factors (such as the background `button_fill` when `as_button` is `TRUE`).
`show_underline`	Show the link underline `⁠scalar<character>\|scalar<logical>⁠` // default: `"auto"` Should the link be decorated with an underline? By default this is `"auto"` which means that gt will choose `TRUE` when `as_button = FALSE` and `FALSE` in the other case. The link underline will be the same color as that set in the `color` option.
`button_fill`, `button_width`, `button_outline`	Button options `⁠scalar<character>⁠` // default: `"auto"` Options for styling a link-as-button (and only applies if `as_button = TRUE`). All of these options are by default set to `"auto"`, allowing gt to choose appropriate fill, width, and outline values.
`target`, `rel`, `referrerpolicy`, `hreflang`	Anchor element attributes `⁠scalar<character>⁠` // default: `NULL` Additional anchor element attributes. For descriptions of each attribute and the allowed values, refer to the MDN Web Docs reference on the anchor HTML element.

Value

An object of class gt_tbl.

Compatibility of formatting function with data values

fmt_url() 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

from_column() can be used with certain arguments of fmt_url() 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():

label
as_button
color
show_underline
button_fill
button_width
button_outline

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 cols_add() (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.

Examples

Using a portion of the towny dataset, let's create a gt table. We can use fmt_url() on the website column to generate navigable links to websites. By default the links are underlined and the color will be chosen for you (it's dark cyan).

towny |>
  dplyr::filter(csd_type == "city") |>
  dplyr::arrange(desc(population_2021)) |>
  dplyr::select(name, website, population_2021) |>
  dplyr::slice_head(n = 10) |>
  gt() |>
  tab_header(
    title = md("The 10 Largest Municipalities in `towny`"),
    subtitle = "Population values taken from the 2021 census."
  ) |>
  fmt_integer() |>
  fmt_url(columns = website) |>
  cols_label(
    name = "Name",
    website = "Site",
    population_2021 = "Population"
  )

This image of a table was generated from the first code example in the `fmt_url()` help file.

Let's try something else. We can set a static text label for the link with the label argument (and we'll use the word "site" for this). The link underline is removable with show_underline = FALSE. With this change, it seems sensible to merge the link to the "name" column and enclose the link text in parentheses (cols_merge() handles all that).

towny |>
  dplyr::filter(csd_type == "city") |>
  dplyr::arrange(desc(population_2021)) |>
  dplyr::select(name, website, population_2021) |>
  dplyr::slice_head(n = 10) |>
  gt() |>
  tab_header(
    title = md("The 10 Largest Municipalities in `towny`"),
    subtitle = "Population values taken from the 2021 census."
  ) |>
  fmt_integer() |>
  fmt_url(
    columns = website,
    label = "site",
    show_underline = FALSE
  ) |>
  cols_merge(
    columns = c(name, website),
    pattern = "{1} ({2})"
  ) |>
  cols_label(
    name = "Name",
    population_2021 = "Population"
  )

This image of a table was generated from the second code example in the `fmt_url()` help file.

fmt_url() allows for the styling of links as 'buttons'. This is as easy as setting as_button = TRUE. Doing that unlocks the ability to set a button_fill color. This color can automatically selected by gt (this is the default) but here we're using "steelblue". The label argument also accepts a function! We can choose to adapt the label text from the URLs by eliminating any leading "https://" or "www." parts.

towny |>
  dplyr::filter(csd_type == "city") |>
  dplyr::arrange(desc(population_2021)) |>
  dplyr::select(name, website, population_2021) |>
  dplyr::slice_head(n = 10) |>
  dplyr::mutate(ranking = dplyr::row_number()) |>
  gt(rowname_col = "ranking") |>
  tab_header(
    title = md("The 10 Largest Municipalities in `towny`"),
    subtitle = "Population values taken from the 2021 census."
  ) |>
  fmt_integer() |>
  fmt_url(
    columns = website,
    label = function(x) gsub("https://|www.", "", x),
    as_button = TRUE,
    button_fill = "steelblue",
    button_width = px(150)
  ) |>
  cols_move_to_end(columns = website) |>
  cols_align(align = "center", columns = website) |>
  cols_width(
    ranking ~ px(40),
    website ~ px(200)
  ) |>
  tab_options(column_labels.hidden = TRUE) |>
  tab_style(
    style = cell_text(weight = "bold"),
    locations = cells_stub()
  ) |>
  opt_vertical_padding(scale = 0.75)

This image of a table was generated from the third code example in the `fmt_url()` help file.

It's perhaps inevitable that you'll come across missing values in your column of URLs. fmt_url() will preserve input NA values, allowing you to handle them with sub_missing(). Here's an example of that.

towny |>
  dplyr::arrange(population_2021) |>
  dplyr::select(name, website, population_2021) |>
  dplyr::slice_head(n = 10) |>
  gt() |>
  tab_header(
    title = md("The 10 Smallest Municipalities in `towny`"),
    subtitle = "Population values taken from the 2021 census."
  ) |>
  fmt_integer() |>
  fmt_url(columns = website) |>
  cols_label(
    name = "Name",
    website = "Site",
    population_2021 = "Population"
  ) |>
  sub_missing()

This image of a table was generated from the fourth code example in the `fmt_url()` help file.

Links can be presented as icons. Let's take a look at an example of this type of presentation with a table based on the films dataset. The imdb_url column contains the URL information and in the fmt_url() call, we can use fontawesome::fa() to specify a label. In this case we elect to use the "link" icon and we can make some sizing adjustments to the icon here to ensure the layout looks optimal. We also use cols_merge() to combine the film's title, its original title (if present), and the link icon.

films |>
  dplyr::filter(year == 2021) |>
  dplyr::select(
    contains("title"), run_time, director, imdb_url
  ) |>
  gt() |>
  tab_header(title = "Feature Films in Competition at the 2021 Festival") |>
  fmt_url(
    columns = imdb_url,
    label = fontawesome::fa(
      name = "link",
      height = "0.75em",
      vertical_align = "0em"
     ),
    color = "gray65"
  ) |>
  cols_merge(
    columns = c(title, original_title, imdb_url),
    pattern = "{1}<< ({2})>> {3}"
  ) |>
  cols_label(
    title = "Film",
    run_time = "Length",
    director = "Director(s)",
  ) |>
  tab_options(heading.title.font.size = px(26)) |>
  opt_vertical_padding(scale = 0.4) |>
  opt_horizontal_padding(scale = 2) |>
  opt_align_table_header(align = "left")

This image of a table was generated from the fifth code example in the `fmt_url()` help file.

Function ID

3-21

Function Introduced

v0.9.0 (Mar 31, 2023)