lt_spanner: Add a column spanner

In lt: Lightweight Tables via JSON Specs and JavaScript

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	Columns to span: character names, integer positions, or a one-sided formula (predicate formulas such as ~ endsWith(., "_time") are also allowed; see lt_align()). 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)

lt documentation built on Oct. 17, 2026, 9:06 a.m.