Controlling the width of data frame tables

Joe Zhu ([shajoezhu])

2026-11-13

Overview

Data frame slides (the small tables made by df_* programs, for example in dose-escalation decks) get their size from autoslider.core, not from the PowerPoint theme. This guide shows how to control:

1. the width of the whole table on the slide, and
2. the width of each column.

Widths are in inches. A 16:9 slide is 13.33 in wide in basic.pptx and 10 in wide in the 10 x 5.625 in dose themes.

How the width is set

When generate_slides() turns a data frame into a table, it works in this order:

1. Size the columns.
   • dose_template = TRUE (dose decks): each column is sized to its content (flextable::autofit()), and the table is shrunk only if it is wider than 10 in (flextable::fit_to_width(10)). A small table stays small: it is not stretched to fill the slide or the placeholder.
   • dose_template = FALSE (the default): the columns take the widths in col_width (when given). If the table is then wider than 10 in, all columns are scaled down to a total of 10.5 in.
2. Apply the table format (table_format, e.g. autoslider_format or a study format).
3. Place the table at table_loc. A placeholder location such as officer::ph_location_label("Content Placeholder 2") sets where the table goes, not how wide it is.

Two things follow from this order:

• col_width only has an effect when dose_template = FALSE.
• Anything the table format does to the widths comes last, so it always wins. A format function is therefore the way to control widths in a dose deck.

Example data and a helper

library(autoslider.core)

cohorts <- data.frame(
  Cohort = c("Cohort 1", "Cohort 2", "Cohort 3"),
  "IMP Dose" = c("10 mg QW", "20 mg QW", "40 mg QW"),
  "No. pts dosed" = c(3, 3, 4),
  "DLT details" = c("None", "Grade 3 rash in one patient", "None"),
  check.names = FALSE
)

The helper below reads the column widths of the table on the last slide of a deck, so we can see what each setting does. It is only for this guide; you do not need it in a study.

slide_col_widths <- function(pptx) {
  dir <- tempfile()
  utils::unzip(pptx, exdir = dir)
  slides <- list.files(file.path(dir, "ppt", "slides"), pattern = "^slide[0-9]+\\.xml$", full.names = TRUE)
  last <- slides[order(as.integer(gsub("\\D", "", basename(slides))))][length(slides)]
  cols <- xml2::xml_find_all(xml2::read_xml(last), "//a:gridCol")
  round(as.numeric(xml2::xml_attr(cols, "w")) / 914400, 2) # EMU to inches
}

make_slide <- function(..., table_format = autoslider_dose_format) {
  out <- tempfile(fileext = ".pptx")
  generate_slides(list(cohorts = cohorts), outfile = out, table_format = table_format, ...)
  out
}

Column widths

Default: sized to the content

In a dose deck each column is as wide as its content needs:

w <- slide_col_widths(make_slide(dose_template = TRUE))
w
#> [1] 0.94 1.09 1.34 2.39
sum(w)
#> [1] 5.76

Set every column with col_width

Give one width per column. This needs dose_template = FALSE:

slide_col_widths(make_slide(dose_template = FALSE, col_width = c(1.2, 1.4, 1, 3)))
#> [1] 1.2 1.4 1.0 3.0

With dose_template = TRUE, col_width is ignored and the columns are sized to their content again:

slide_col_widths(make_slide(dose_template = TRUE, col_width = c(1.2, 1.4, 1, 3)))
#> [1] 0.94 1.09 1.34 2.39

Note that dose_template = FALSE also builds the header from the data frame’s variable labels (or the column names when there are none).

Set some columns in a table format

To keep the dose layout and change just the columns you care about, set their width in a table format. A format receives the slide’s font sizes (body_font_size, footer_font_size, …) through .... Only pass ... on to a format that accepts them, such as autoslider_format() or a study format with those arguments; autoslider_dose_format() does not, so the examples here call it with ft alone.

Columns can be named or numbered:

wide_dlt_format <- function(ft, ...) {
  ft <- autoslider_dose_format(ft)
  flextable::width(ft, j = "DLT details", width = 3.5)
}

slide_col_widths(make_slide(dose_template = TRUE, table_format = wide_dlt_format))
#> [1] 0.94 1.09 1.34 3.50

Only the “DLT details” column changed; the others keep their content width.

Table width

Shrink a wide table

flextable::fit_to_width() scales the columns down so the table is at most max_width inches wide. It never makes a table wider.

narrow_format <- function(ft, ...) {
  ft <- autoslider_dose_format(ft)
  flextable::fit_to_width(ft, max_width = 4)
}

w <- slide_col_widths(make_slide(dose_template = TRUE, table_format = narrow_format))
w
#> [1] 0.60 0.70 0.94 1.53
sum(w)
#> [1] 3.77

Stretch a table to a set width

To make a small table fill the slide, scale all columns so they add up to the width you want. The columns keep their relative sizes:

table_width <- function(ft, width) {
  widths <- flextable::flextable_dim(ft)$widths
  flextable::width(ft, width = dim(ft)$widths * width / widths)
}

full_width_format <- function(ft, ...) {
  ft <- autoslider_dose_format(ft)
  table_width(ft, width = 9)
}

w <- slide_col_widths(make_slide(dose_template = TRUE, table_format = full_width_format))
w
#> [1] 1.47 1.71 2.09 3.73
sum(w)
#> [1] 9

On a 10 in dose slide, 9 in leaves a 0.5 in margin each side when the table starts 0.5 in from the left edge.

Fixed widths for every column

A format can also give every column a fixed width. The number of widths must match the number of columns, so this only suits a format used by one table:

cohort_table_format <- function(ft, ...) {
  ft <- autoslider_dose_format(ft)
  flextable::width(ft, width = c(1.2, 1.4, 1, 4.5))
}

slide_col_widths(make_slide(dose_template = TRUE, table_format = cohort_table_format))
#> [1] 1.2 1.4 1.0 4.5

Using this in a dose speclayout

Put the format functions in the study’s R/formats.R (which run_slides.R sources), then name them per slide in dose_speclayout.yml. Keep the font-size arguments so a per-slide font_size: block still reaches the format:

# R/formats.R
full_width_gred <- function(ft, body_font_size = 8, header_font_size = 8, ...) {
  ft <- black_format_gred(ft, body_font_size = body_font_size, header_font_size = header_font_size, ...)
  widths <- flextable::flextable_dim(ft)$widths
  flextable::width(ft, width = dim(ft)$widths * 9 / widths)
}

# Stretch this table to 9 in.
df_all_cohorts_demo1_DM:
  program: df_all_cohorts_demo1
  suffix: DM
  table_format: full_width_gred
  table_loc: officer::ph_location_label("Content Placeholder 2")

# Or set the column widths directly, without the dose layout.
df_patient_overview_slide_DM:
  program: df_patient_overview_slide
  suffix: DM
  dose_template: FALSE
  col_width: c(0.8, 0.8, 1.2, 1.5, 1, 1, 2)

Values in a dose speclayout are evaluated as R code, so col_width is written as c(...).

Summary

Goal	Dose deck (dose_template = TRUE)	dose_template = FALSE
Widths of all columns	Table format: flextable::width(ft, width = c(...))	col_width = c(...)
Width of one column	Table format: flextable::width(ft, j = "name", width = )	Table format, as for dose decks
Shrink the table to a maximum	Table format: flextable::fit_to_width(ft, max_width = ) (wider than 10 in is shrunk automatically)	Automatic above 10 in (scaled to 10.5 in)
Stretch the table to a width	Table format: scale dim(ft)$widths to the total you want	Same, or choose col_width to add up to it

Table position comes from table_loc; width comes from the steps above. See also vignette("using_formats") for colors, fonts and borders.