Exporting flextable Tables to PDF • writetfl

This vignette covers export_tfl() as used with flextable objects. For data-frame tables built with tfl_table(), see vignette("v02-tfl_table_intro"). For gt tables, see vignette("v05-gt_tables"). For rtables tables, see vignette("v06-rtables"). For figure output, see vignette("v01-figure_output").

library(writetfl)
library(flextable)
library(grid)

Basic usage

Pass a flextable object directly to export_tfl(). Captions set via set_caption() are automatically extracted and placed in writetfl’s caption zone. Footer rows (from footnote() or add_footer_lines()) are extracted into writetfl’s footnote zone.

ft <- flextable(head(iris, 10)) |>
  set_caption("Iris Measurements — First 10 Rows") |>
  add_footer_lines("Source: Anderson (1935).")

export_tfl(ft, preview = TRUE)

Caption handling

The caption from set_caption() is placed in writetfl’s caption section above the table. It does not appear in the gen_grob() output (flextable reserves captions for document formats like Word and HTML), so there is no duplication.

ft <- flextable(head(mtcars[, 1:6], 8)) |>
  set_caption("Table 1. Selected Motor Trend Variables")

export_tfl(ft, preview = TRUE,
  header_left = "Appendix A",
  header_rule = TRUE,
  footer_rule = TRUE
)

Footnote extraction

Footer rows added via footnote() or add_footer_lines() are extracted as plain text and placed in writetfl’s footnote zone below the table. The footer rows are removed from the flextable before rendering so they don’t appear twice.

When footnote() is used, the superscript reference symbols in body cells are preserved — they still point to the footnotes now positioned in writetfl’s footnote section.

ft <- flextable(head(iris, 8)) |>
  set_caption("Table 2. Iris with Footnotes")

ft <- footnote(ft, i = 1, j = 1, part = "body",
  value = as_paragraph("Measured in centimetres."),
  ref_symbols = "a"
)
ft <- footnote(ft, i = 1, j = 3, part = "body",
  value = as_paragraph("Petal measurements are less variable."),
  ref_symbols = "b"
)

export_tfl(ft, preview = TRUE,
  header_left  = "Study Report",
  header_rule  = TRUE,
  footer_rule  = TRUE
)

Adding page layout elements

All of writetfl’s page layout arguments work with flextable tables. Pass them via ... just as you would for figures.

ft <- flextable(head(mtcars[, 1:6], 10)) |>
  set_caption("Table 3. Motor Trend Cars") |>
  add_footer_lines("Source: Motor Trend (1974).")

export_tfl(
  ft,
  preview      = TRUE,
  header_left  = "Study Report",
  header_right = format(Sys.Date(), "%d %b %Y"),
  header_rule  = TRUE,
  footer_rule  = TRUE
)

Multiple flextable tables

Pass a list of flextable objects to produce a multi-page PDF with one table per page.

ft1 <- flextable(head(iris, 10)) |>
  set_caption("Table 1. Iris (first 10 rows)")

ft2 <- flextable(tail(iris, 10)) |>
  set_caption("Table 2. Iris (last 10 rows)")

export_tfl(
  list(ft1, ft2),
  file         = "two-tables.pdf",
  header_left  = "Appendix",
  header_rule  = TRUE
)

Automatic pagination

When a flextable table is too tall to fit on a single page, export_tfl() splits it across pages by subsetting body rows. The header is repeated on each page, and caption and footnote are carried through to every page.

big_data <- data.frame(
  ID     = seq_len(60),
  Name   = paste("Subject", seq_len(60)),
  Age    = sample(25:75, 60, replace = TRUE),
  Weight = round(rnorm(60, 70, 12), 1),
  Score  = round(runif(60, 50, 100), 1),
  Group  = rep(c("Treatment", "Control"), each = 30)
)

big_ft <- flextable(big_data) |>
  set_caption("Table 5. Subject Listing — Full Cohort") |>
  add_footer_lines("Source: Simulated clinical trial data.") |>
  theme_booktabs()

export_tfl(
  big_ft,
  preview      = 1:2,
  header_left  = "Analysis Report",
  header_rule  = TRUE,
  footer_rule  = TRUE
)

Note: When pagination occurs, per-cell formatting applied via color(), bg(), bold(), etc. is not preserved on paginated pages. Themes (e.g., theme_vanilla()) are not re-applied. For tables with extensive cell-level formatting, ensure the table fits on a single page or split the data manually before creating flextable objects.

Preserved features

The following flextable features are preserved through the gen_grob() rendering pipeline:

Feature	Preserved?	Notes
`set_caption()`	Yes	Extracted as writetfl caption
`footnote()`	Yes	Text extracted as writetfl footnote; reference symbols preserved in cells
`add_footer_lines()`	Yes	Extracted as writetfl footnote
`add_header_row()`	Yes	Rendered as part of table header
`add_header_lines()`	Yes	Rendered as part of table header
`set_header_labels()`	Yes	Column header labels
`merge_v()`, `merge_h()`, `merge_at()`	Yes	Cell merging
`border()`, `hline()`, `vline()`	Yes	All border styles
`color()`, `bg()`	Yes	Text and background colours
`bold()`, `italic()`	Yes	Text emphasis
`align()`, `align_text_col()`	Yes	Cell alignment
`theme_*()` functions	Yes	All built-in themes
`colformat_*()` functions	Yes	Number/date formatting
`width()`, `height()`	Yes	Column widths scaled to fit page
`as_image()`, `as_raster()`	Partial	Images render but require appropriate device
`as_equation()`	No	Equations not supported in grid rendering
`hyperlink_text()`	No	Hyperlinks not supported in grid/PDF

Themes

ft <- flextable(head(iris, 8)) |>
  set_caption("Table with Booktabs Theme") |>
  theme_booktabs()

export_tfl(ft, preview = TRUE)

Merged cells

ft <- flextable(head(iris, 8)) |>
  set_caption("Table with Merged Cells") |>
  merge_v(j = "Species")

export_tfl(ft, preview = TRUE)

Borders and colours

ft <- flextable(head(mtcars[, 1:5], 6)) |>
  set_caption("Table with Custom Borders") |>
  border_outer(border = officer::fp_border(width = 2)) |>
  bg(i = 1, bg = "#E8F0FE", part = "header")

export_tfl(ft, preview = TRUE)