Package {lt}

Type: Package
Title: Lightweight Tables via JSON Specs and JavaScript
Version: 0.2
Description: A lightweight grammar of tables. Build a table by declaring a JSON spec (titles, spanners, row groups, footnotes, formatting functions, etc.); a tiny vanilla JavaScript runtime builds the HTML table from the spec on page load. No 'sass', no 'V8', no 'htmlwidgets' — just base R and 'xfun' ('htmltools' is used only for the optional Shiny binding).
License: MIT + file LICENSE
URL: https://github.com/yihui/lt
BugReports: https://github.com/yihui/lt/issues
Depends: R (≥ 4.1.0)
Encoding: UTF-8
Imports: xfun (≥ 0.60)
Suggests: htmltools, knitr, litedown, magick, repr, shiny, testit
Config/lt.js: 1.14.67
Config/roxygen2/version: 8.0.0
NeedsCompilation: no
Packaged: 2026-07-09 20:21:06 UTC; yihui
Author: Yihui Xie ORCID iD [aut, cre, cph] (URL: https://yihui.org)
Maintainer: Yihui Xie <xie@yihui.name>
Repository: CRAN
Date/Publication: 2026-07-09 21:00:02 UTC

lt: Lightweight Tables via JSON Specs and JavaScript

Description

A small grammar of tables. A table is a data frame plus a list of operations (title, spanner, footnote, ...); the operations are serialized to a JSON spec and applied to a plain semantic HTML table by a tiny vanilla JavaScript runtime at render time.

Author(s)

Maintainer: Yihui Xie xie@yihui.name (ORCID) (URL: https://yihui.org) [copyright holder]

Authors:

See Also

Useful links:

Render an lt_tbl to HTML

Description

Emits the CSS+JS runtime and a script block carrying the table's JSON spec. Multiple tables on the same page only need the runtime once.

Usage

## S3 method for class 'lt_tbl'
format(x, fragment = TRUE, inline_assets = TRUE, assets = TRUE, ...)

Arguments

x

An lt_tbl object.

fragment

If TRUE (default), return an HTML fragment suitable for embedding. If FALSE, wrap in a minimal ⁠<html><body>⁠ document.

inline_assets

If TRUE (default), inline the CSS/JS as text. If FALSE, emit ⁠<link>⁠ / ⁠<script src=...>⁠ tags (assets must be served alongside the HTML).

assets

Which runtime assets to include: TRUE (default) for both CSS and JS, FALSE for neither, or a character vector subset of c("css", "js") for selective inclusion.

...

Reserved for future use.

Value

A character scalar containing HTML.

Examples

tbl = lt(head(mtcars))
html = format(tbl)
format(tbl, fragment = FALSE, inline_assets = FALSE)

Create a Table Specification

Description

Entry point of the lightweight grammar of tables. Returns an object (a list) that records the data plus a list of table-modifying operations. The object is rendered to HTML by format() (called automatically by the print method).

Usage

lt(data, ...)

## Default S3 method:
lt(data, auto_format = TRUE, auto_label = TRUE, ...)

Arguments

data

A data frame (or anything coercible to one).

...

Arguments passed to methods.

auto_format

Whether to automatically format numeric columns (rounding, thousand separators, percentage detection). Set to FALSE to disable for the whole table; use lt_format() on specific columns to disable selectively.

auto_label

Whether to automatically clean column names for display by replacing separators (. and ⁠_⁠) with spaces. Set to FALSE to show raw column names.

Value

A table object that can be piped into ⁠lt_*()⁠ functions.

HTML in cells

By default all cell values and text (titles, labels, footnotes, ...) are HTML-escaped, so special characters like <, >, and & render as literal text. To emit content as raw HTML instead:

Interactivity

When a cell value has been formatted (e.g., by auto-formatting or lt_format()), the original value is stored in the cell's title attribute and shown as a tooltip on hover. Additionally:

Raw values are shown as (value) after the formatted text, highlighted with a light yellow background.

Examples

lt(head(mtcars[, 1:4]))

Set Column Alignment

Description

Override the auto-detected alignment for specific columns. By default, numeric columns are right-aligned and character columns are left-aligned.

Usage

lt_align(x, columns, align = c("left", "center", "right"))

Arguments

x

An lt() object.

columns

Character vector of column names (or a one-sided formula).

align

One of "left", "center", or "right".

Value

x with the alignment recorded.

Examples

lt(head(mtcars)) |> lt_align(~ cyl + gear, "center")

Attach Custom CSS

Description

Add user-supplied stylesheets or inline rules that render after the built-in CSS, so rules can override the defaults.

Usage

lt_css(x, ...)

Arguments

x

An lt() object.

...

Unnamed arguments are stylesheet paths or URLs. A bare filename (no directory component) that does not exist in the working directory is resolved against the stylesheets shipped with lt, so e.g. lt_css(x, "lt-gt.css") uses the bundled gt-like theme.

Named arguments define inline CSS rules scoped to .lt-table. Names are selectors (e.g., .na, td.highlight) and values are either a CSS string or a named list of properties: lt_css(x, .na = "background: #eee") or lt_css(x, .na = list(background = "#eee")).

Value

x with the stylesheets recorded.

Examples

tbl = lt(head(mtcars))
tbl |>
  lt_style("mpg", test = "v => v > 20", class = "high") |>
  lt_css(.high = list(background = "#cfc", fontWeight = "bold"))

Format Date/Time Columns

Description

Format date or datetime columns using JavaScript's native Date methods. The underlying data should be Date or POSIXt in R (serialized as ⁠new Date(...)⁠ for the browser).

Usage

lt_date(x, columns, method = NULL, locale = NULL, options = NULL)

Arguments

x

An lt() object.

columns

Column selection (formula, character, or numeric).

method

A JS Date method name to call (e.g., "toLocaleDateString", "toISOString", "toDateString", "toLocaleString", "toLocaleTimeString"). If NULL (the default), toLocaleDateString() is used with locale and options. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date#instance_methods for all available methods.

locale

A BCP 47 locale string (e.g., "en-US", "de-DE", "ja-JP"). Only used when method is NULL. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#locales_argument for details.

options

A named list of Intl.DateTimeFormat options. Common fields include year ("numeric", "2-digit"), month ("numeric", "2-digit", "long", "short", "narrow"), day ("numeric", "2-digit"), hour, minute, second ("numeric", "2-digit"), weekday ("long", "short", "narrow"), and timeZoneName ("long", "short"). Only used when method is NULL.

Value

x with the date formatting recorded.

Note

The formatted date may differ from the input date depending on the viewer's local timezone. JavaScript's ⁠new Date("2024-01-15")⁠ parses date-only strings as UTC midnight, but toLocaleDateString() converts to the local timezone. For example, 2024-01-15 will display as 2024-01-14 for a viewer at GMT-6. To avoid this, pass options = list(timeZone = "UTC").

Examples

d = data.frame(
  event = c("Launch", "Update"),
  date = as.Date(c("2024-01-15", "2024-06-30"))
)
lt(d) |> lt_date(~ date)
lt(d) |> lt_date(~ date, options = list(year = "numeric", month = "short"))

Export an lt table to a file

Description

Save a table to disk. The output format is chosen from the file extension of output: .html writes an HTML table, .pdf writes a vector PDF, and any other extension writes a PNG. PDF and PNG are produced by rendering the table in a headless Chromium browser (via xfun::browser_print()).

Usage

lt_export(
  x,
  output = "lt.html",
  method = c("auto", "node", "browser", "raw"),
  css = TRUE,
  fragment = FALSE,
  tidy = FALSE,
  crop = TRUE,
  width = NULL,
  padding = 8,
  browser = NULL,
  ...
)

Arguments

x

An lt_tbl object.

output

Output file path. Its extension selects the format: .html, .pdf, or (otherwise) PNG. If NA, the HTML is returned as a string instead of being written to a file.

method

How to produce the HTML ⁠<table>⁠: "auto", "node", "browser", or "raw" (see Details). Applies only to .html output.

css

Whether to include the lt.css runtime stylesheet in the HTML output. User CSS from lt_css() is always included. Applies only to .html output.

fragment

If FALSE (default), wrap the HTML in a full HTML document; if TRUE, return only the table fragment. Applies only to .html output.

tidy

Whether to pretty-print the baked ⁠<table>⁠ with line breaks and indentation. Applies only to .html output baked by "node" or "browser" (ignored for method = "raw", which is a JavaScript spec).

crop

Whether to crop the PDF/PNG tightly to the table, removing the surrounding page whitespace. This adds a preliminary browser pass to measure the rendered table. Set to FALSE for the default full page. Cropping PNG output requires the magick package; without it, PNG falls back to the full page (with a warning).

width

The width of the table in CSS pixels. By default (NULL) it shrinks to the table's natural width. A smaller width wraps cell content; a larger one pads the table.

padding

Padding in CSS pixels to keep around the table when cropping. A single value (all sides) or a length-two vector c(vertical, horizontal).

browser

Path to the Chromium-based browser; passed to xfun::browser_print(). NULL (default) auto-detects.

...

Passed to xfun::browser_print() for PDF/PNG output.

Details

For .html output, method controls how the ⁠<table>⁠ is produced: "raw" writes the JavaScript-spec HTML, so the table is built in the browser by the lt.js runtime when the file is viewed; the other methods bake a static ⁠<table>⁠ up front by running lt.js once (via "node" in Node.js or "browser" in a headless Chromium browser; "auto" picks Node if available, else the browser), so the saved file needs no JavaScript to view. method, css, fragment, and tidy apply only to .html output.

Value

The output path, or (when output is NA) the HTML as a string.

Global option

When the option lt.lt_static is set to a list of arguments (e.g., options(lt.lt_static = list(css = FALSE))), the knit_print and record_print methods emit the same static HTML table as lt_export(x, "*.html") (using those arguments as method/css/fragment) instead of the default JavaScript-based spec. This is useful for output formats that support raw HTML but cannot run JavaScript (e.g., GitHub Flavored Markdown).

Examples

tbl = lt(head(mtcars))

# HTML with the JavaScript spec (table built by lt.js when viewed)
lt_export(tbl, NA, method = 'raw')  # character output
f1 = tempfile(fileext = '.html')
lt_export(tbl, f1, method = 'raw')  # file output

# Bake a static <table> (needs Node.js or a headless browser).
if (lt:::can_bake())
  lt_export(tbl, NA, method = 'auto', fragment = TRUE, css = FALSE)

# PDF / PNG are rendered in a headless browser and cropped to the table.
f2 = tempfile(fileext = '.pdf')
f3 = tempfile(fileext = '.png')
if (lt:::has_browser()) {
  lt_export(tbl, f2)
  lt_export(tbl, f3, width = 400)
}

unlink(c(f1, f2, f3))

Add a Footnote

Description

Attaches a footnote text to a table region. Footnotes are numbered automatically in the order they are added (de-duplicated by text).

Usage

lt_footnote(x, text, where, columns = NULL, rows = NULL, match = NULL)

Arguments

x

An lt() object.

text

Footnote text.

where

One of 'title', 'subtitle', 'column', 'spanner', 'group', or 'body'.

columns

Character vector of column names or a one-sided formula (for 'column' or 'body'). For 'group' with match = "starts_with", a single prefix string.

rows

Integer vector of 1-based row indices (for 'body'; NULL means all rows).

match

For where = "group": one of "exact" (default), "starts_with", or "all".

Value

x with the footnote recorded.

Examples

lt(head(mtcars)) |>
  lt_footnote("Source: 1974 Motor Trend US magazine.", "title")
# raw HTML footnote (wrap in I())
lt(head(mtcars)) |>
  lt_footnote(I("See <a href='#'>docs</a>."), "title")

Format Numeric Columns

Description

Control the number of decimal places and thousands separator for numeric columns. Columns passed to this function are excluded from automatic formatting (see the auto_format argument of lt()). To disable auto-format for a column without otherwise changing its display, call lt_format(x, ~col) with no other arguments.

Usage

lt_format(
  x,
  columns,
  decimals = NULL,
  big_mark = NULL,
  percent = NULL,
  prefix = NULL,
  suffix = NULL
)

Arguments

x

An lt() object.

columns

Character or integer vector of columns (or a one-sided formula).

decimals

Number of decimal places (default NULL means no change).

big_mark

Thousands separator (e.g., ","). NULL or "" means none.

percent

If TRUE, multiply values by 100 and append "%". If "%", only append "%" without multiplying (for values already in percent scale).

prefix

String prepended to each formatted value (e.g., "$").

suffix

String appended to each formatted value (e.g., " kg").

Value

x with the formatting recorded.

Examples

lt(head(mtcars)) |> lt_format(~ mpg + wt, decimals = 1, big_mark = ",")
d = data.frame(Item = c("A", "B"), Price = c(1234.5, 678.9))
lt(d) |> lt_format(~ Price, decimals = 2, big_mark = ",", prefix = "$")

Define Row Groups

Description

Partition rows into labeled groups. Pass column names to group by those columns' values (the columns are removed from the body and rendered as rowspan cells on the left). Use sep = TRUE to render groups as full-width separator rows instead of rowspan.

Usage

lt_group(x, ..., sep = "auto", sort = TRUE)

Arguments

x

An lt() object.

...

A column name or formula (e.g., ~col or ~col1 + col2) to group by column values, or named arguments of the form "Label" = rows (integer vector of 1-based row indices) for manual groups. Unnamed character strings reorder previously defined groups.

sep

If TRUE, render groups as full-width separator rows instead of the default rowspan style. Only supports a single grouping column. The default 'auto' uses separator rows when there is a single character grouping column with any value longer than 20 characters (numeric columns always use rowspan).

sort

If TRUE (default), sort rows by group columns so that identical group values are contiguous. Set to FALSE to preserve the original row order.

Value

x with the row groups recorded.

Examples

# Group by a column (rowspan, default)
d = data.frame(arm = c("Placebo", "Placebo", "Treatment", "Treatment"),
               stat = c("n", "Mean", "n", "Mean"), value = c(30, 4.2, 31, 6.8))
lt(d) |> lt_group(~ arm)

# Separator-row style
lt(d) |> lt_group(~ arm, sep = TRUE)

# Manual groups (always separator rows)
lt(head(mtcars)) |>
  lt_group("First three" = 1:3, "Last three" = 4:6)

Add a Title and Subtitle

Description

Add a Title and Subtitle

Usage

lt_header(x, title = NULL, subtitle = NULL)

Arguments

x

An lt() object.

title

A character scalar. Wrap in I() to treat as raw HTML.

subtitle

A character scalar. Wrap in I() to treat as raw HTML.

Value

x with the header recorded.

Examples

lt(head(mtcars)) |> lt_header("Motor Trend Cars", "First 6 rows")
# raw HTML title
lt(head(mtcars)) |> lt_header(I("<em>Motor Trend</em> Cars"))

Render Column Cells as Raw HTML

Description

Mark whole columns so their body cells are emitted as raw HTML instead of being escaped. By default every cell is HTML-escaped (so <, >, and & render as literal text); use this to embed links, emphasis, or other markup in a column's cells.

Usage

lt_html(x, columns)

Arguments

x

An lt() object.

columns

Column names (character or one-sided formula) whose cells are raw HTML. If missing, all columns are treated as raw HTML.

Details

To emit raw HTML in other regions (title, column labels, footnotes, ...), wrap the text in I() in the corresponding ⁠lt_*()⁠ function instead.

Value

x with the raw-HTML columns recorded.

Examples

d = data.frame(
  name = c("<a href='#a'>A</a>", "<a href='#b'>B</a>"), n = 1:2
)
lt(d) |> lt_html(~ name)

Indent Rows

Description

Add hierarchical indentation to the first column of specified rows.

Usage

lt_indent(x, rows, level = 1)

Arguments

x

An lt() object.

rows

Integer vector of 1-based row indices to indent.

level

Indent level (default 1). Each level adds one unit of left padding.

Value

x with the indentation recorded.

Examples

d = data.frame(label = c("Overall", "Male", "Female"), n = c(100, 55, 45))
lt(d) |> lt_indent(2:3)

Rename Column Labels

Description

Override column headers without modifying the underlying data frame.

Usage

lt_label(x, ...)

Arguments

x

An lt() object.

...

Named arguments of the form col_name = "Display Label". Wrap a label in I() to treat it as raw HTML.

Value

x with the column label overrides recorded.

Examples

lt(head(mtcars)) |> lt_label(mpg = "Miles/Gallon", cyl = "Cylinders")
# raw HTML label (wrap in I())
lt(head(mtcars)) |> lt_label(mpg = I("Miles/Gallon<sup>*</sup>"))

Merge Columns

Description

Combine values from multiple columns into a single display column using a pattern. Source columns (all except the first) are hidden by default.

Usage

lt_merge(x, columns, pattern = NULL, hide = TRUE)

Arguments

x

An lt() object.

columns

Character vector of column names (or a one-sided formula). The first column is the target (receives merged content); the rest are sources.

pattern

A glue-style template using ⁠\{1\}⁠, ⁠\{2\}⁠, etc. to refer to columns by position. Wrap sections in ⁠<<⁠ and ⁠>>⁠ for conditional NA handling: "\{1\}<< (\{2\})>>" drops the wrapped portion when any referenced value is missing/empty. If NULL, columns are concatenated separated by spaces.

hide

If TRUE (default), source columns (all but the first) are automatically hidden.

Value

x with the merge recorded.

Examples

d = data.frame(stat = c("Mean", "SD"), value = c(4.2, 1.1), ci = c("(2.0, 6.4)", "(0.5, 1.7)"))
lt(d) |> lt_merge(~ value + ci, pattern = "{1} {2}")

Move Columns

Description

Rearrange column display order without modifying the data frame.

Usage

lt_move(x, columns, after = NULL)

Arguments

x

An lt() object.

columns

Character vector of column names (or a one-sided formula).

after

Column name after which to place the moved columns. Use NULL to move to the start.

Value

x with the column move recorded.

Examples

lt(head(mtcars)) |> lt_move(~ gear + carb, after = "mpg")

Add a Note

Description

Notes are rendered in the table footer below numbered footnotes.

Usage

lt_note(x, text)

Arguments

x

An lt() object.

text

Note text. Wrap in I() to treat as raw HTML.

Value

x with the note recorded.

Examples

lt(head(mtcars)) |> lt_note("CI = confidence interval.")
# raw HTML note (wrap in I())
lt(head(mtcars)) |> lt_note(I("CI = <em>confidence interval</em>."))

Shiny Bindings for lt

Description

lt_output() creates a UI placeholder; render_lt() supplies the table spec from the server. Together they render an lt() table as a custom Shiny output — no renderUI() involved.

Usage

lt_output(outputId, ...)

render_lt(expr, env = parent.frame(), quoted = FALSE)

Arguments

outputId

Output variable name to read the table from.

...

Reserved for future use.

expr

An expression that returns an lt() object.

env

Environment in which to evaluate expr.

quoted

Whether expr is already quoted.

Value

lt_output() returns a Shiny UI element; render_lt() returns a render function.

Examples

if (interactive()) {
library(shiny)
ui = fluidPage(lt_output("tbl"))
server = function(input, output) {
  output$tbl = render_lt(lt(head(mtcars)) |> lt_header("Motor Trend"))
}
shinyApp(ui, server)
}

Add a Column Spanner

Description

A spanner is a label rendered above a contiguous group of column headers.

Usage

lt_spanner(x, label, columns, sep = "[._]")

Arguments

x

An lt() object.

label

A character scalar — the spanner text. Alternatively, a two-sided formula Label ~ col1 + col2 providing both the label (LHS) and columns (RHS). When missing, spanners are inferred from column names.

columns

Column names (character or formula). When missing, inferred from column names.

sep

Separator pattern for auto-inference (default "[._]").

Details

When called with no label or columns, infers spanners from column names by splitting on the first . or ⁠_⁠ separator. Contiguous columns sharing a prefix are grouped under that prefix, and column labels are shortened to the suffix.

Value

x with the spanner recorded.

Note

The columns must be contiguous in the body of the table.

Examples

tbl = lt(head(iris))
# Explicit spanner
tbl |> lt_spanner(Sepal ~ Sepal.Length + Sepal.Width)
# Auto-infer from column names
tbl |> lt_spanner()
# raw HTML label (wrap in I())
tbl |> lt_spanner(I("<em>Sepal</em>"), ~ Sepal.Length + Sepal.Width)

Style Cells

Description

Apply CSS styling to specific cells. Target cells by column, row, or both. When test is provided, styles are applied conditionally based on cell values (evaluated in JavaScript).

Usage

lt_style(
  x,
  columns = NULL,
  rows = NULL,
  test = NULL,
  class = NULL,
  bold = NULL,
  italic = NULL,
  color = NULL,
  bg = NULL,
  ...
)

Arguments

x

An lt() object.

columns

Character vector of column names, a one-sided formula, or NULL for all.

rows

Integer vector of 1-based row indices (or NULL for all).

test

A JavaScript function as a string (e.g., "v => v < 0") that receives the raw cell value and returns true to apply the style. When NULL, the style applies unconditionally.

class

CSS class name(s) to add to matching cells. Define the corresponding rules in an external stylesheet via lt_css().

bold

Logical: apply bold weight?

italic

Logical: apply italic style?

color

Text color (any CSS color value, e.g., "red", "#06c").

bg

Background color.

...

Additional CSS properties as named arguments. Names can be camelCase (e.g., borderLeft) or quoted dash-case (e.g., `border-left`). Values are CSS strings.

Value

x with the style recorded.

Examples

tbl = lt(head(mtcars))
tbl |>
  lt_style("mpg", rows = 1L, bold = TRUE, borderBottom = "2px solid red")
tbl |>
  lt_style("mpg", test = "v => v > 20", class = "high") |>
  lt_css(.high = list(background = "#cfc"))

Substitute Cell Values

Description

Replace NA, zero, or small values with display text.

Usage

lt_sub(
  x,
  columns = NULL,
  missing = NULL,
  zero = NULL,
  small = NULL,
  small_text = NULL
)

Arguments

x

An lt() object.

columns

Character vector of column names, a one-sided formula, or NULL for all.

missing

Replacement for NA cells (e.g., "—"). NULL to leave NAs as empty strings (the default rendering).

zero

Replacement for zero values (e.g., "—").

small

Threshold: values whose absolute value is below this are replaced by small_text.

small_text

Text shown for values below small (e.g., "<0.1").

Value

x with the substitution recorded.

Examples

d = data.frame(x = c(1, 0, NA, 0.001))
lt(d) |> lt_sub(missing = "—", zero = "—", small = 0.01, small_text = "<0.01")

Set Column Widths

Description

Set Column Widths

Usage

lt_width(x, ...)

Arguments

x

An lt() object.

...

Named arguments of the form col_name = "width". Width can be any CSS value (e.g., "100px", "20%", "8em").

Value

x with the column widths recorded.

Examples

lt(head(mtcars)) |> lt_width(mpg = "100px", cyl = "50px")

Print an lt_tbl (Opens in the Viewer or Browser)

Description

Print an lt_tbl (Opens in the Viewer or Browser)

Usage

## S3 method for class 'lt_tbl'
print(x, ...)

Arguments

x

An lt_tbl object.

...

Passed to format().

Value

x, invisibly.

Examples

print(lt(head(mtcars)))