Merge headers in flextables created from gtsummary objects

Vertically extends visible header cells through contiguous blank padding cells immediately above them when the resulting merged area is rectangular. Ordinary column labels and spanning headers are treated equally.

Usage

merge_headers(x)

Arguments

x

A flextable object, typically produced by gtsummary::as_flex_table().

Value

The modified flextable object.

Details

This function is intended primarily for flextable objects produced by gtsummary::as_flex_table(), which uses " " (a single space) for missing spanning-header cells. A cell containing exactly " " is therefore treated as structural padding. Call this function immediately after conversion and before applying additional header styling.

Existing horizontal blank spans are split only where required for a vertical merge. Header content is never crossed, and cells that are already merged vertically are left unchanged.

Examples

gtsummary::tbl_summary(
  gtsummary::trial,
  by = "trt",
  include = c("age", "marker")
) |>
  gtsummary::modify_spanning_header(
    gtsummary::all_stat_cols() ~ "**Treatment Received**"
  ) |>
  gtsummary::as_flex_table() |>
  merge_headers()
Characteristic
Treatment Received
Drug A  
N = 981
Drug B  
N = 1021
Age
46 (37, 60)
48 (39, 56)
Unknown
7
4
Marker Level (ng/mL)
0.84 (0.23, 1.60)
0.52 (0.18, 1.21)
Unknown
6
4
1Median (Q1, Q3)