Chapter 8 Cell content

By default, the displayed content of each cell will be the result of a simple formatting. The content can also be composed as the result of a concatenation of several chunks.

The tables will all display cell contents representing the contents of the corresponding input data.frame cell. If it’s a string, it will remain as is, if it’s a number, it will be transformed into a string with a certain number of decimal places, if it’s a date, it will be transformed into a string representing a date, and so on.

The default display is conditioned by the type of data, i.e. columns of type double will be formatted with colformat_double(), columns of type integer will be formatted with colformat_int(), columns of type character will be formatted with colformat_char() and so on.

We will first explain the use of the colformat_* functions and then we will see how to create fill cells with richer contents (i.e. being able to mix images, texts and hyperlinks) with the compose(as_paragraph()) functions. Function compose() is also existing in package ‘purrr’ and that causes many troubles, so function mk_par() has been created to avoid that issue. flextable::mk_par() and flextable::compose() are the same exact functions. We will only use mk_par() in this book.

Before showing tables, let’s specify their post-processing before printing with function autofit():

set_flextable_defaults(
  post_process_html = autofit,
  post_process_pdf = autofit,
  post_process_docx = autofit
  )

8.1 Soft returns and tabulations

A cell is made of one single paragraph of text. Paragraphs can contain several chunks of text with different formatting but also images. (see keypoints)

When working with flextable, if a string contains \n or \t, it will be treated as a soft return (not a new paragraph!) or a tabulation.

We don’t recommand to change your data so that it contains \n or \t. Instead we recommand to use mk_par(), prepend_chunks() or append_chunks(). See [#multi-content] for more details about these functions.

dat <- data.frame(a = c("Grand total", letters[1:4]))
flextable(dat) |>
  prepend_chunks(i = ~ a != "Grand total", j = "a", as_chunk("\t"))

a
Grand total
a
b
c
d

8.2 Simple formatting of cell content

Theses are high level functions that should satisfy most of the usual needs. They can be used to define the formatting of one or more columns and eventually on a subset of rows.

Each accept a prefix and suffix argument that can be used to add a currency symbol for example. Also they all have na_str argument (defaut to ““), the string to use when data are not available.

colformat_num() let you format columns of type numeric as it is formatted in your R console. This is the default function applied to all numeric columns when a flextable is created. It does not support digits argument, it uses default R options through calls to format().
colformat_double() with arguments digits and big.mark: let you format columns of type double.
colformat_int() with arguments big.mark: let you format columns of type integer.
colformat_char(): let you format columns of type character.
colformat_lgl(): let you format columns of type logical.
colformat_image(): let you format image paths as images.
colformat_date() and colformat_datetime(): let you format columns of type date and datetime (POSIX).

The following illustration is using dataset “people” (see table 15.4).

flextable(people) %>% 
  colformat_num(
    big.mark = " ", decimal.mark = ",",
    na_str = "na") %>% 
  colformat_int(big.mark = " ") %>% 
  colformat_char(j = "eye_color", prefix = "color: ") %>% 
  colformat_date(fmt_date = "%d/%m/%Y")

name	birthday	n_children	weight	height	n_peanuts	eye_color
Susan Marié-David	18/05/2006	4	88,53768	162,6927	571 239	color: blue
Valentine Lemonnier	29/01/2040	1	na	171,4610	1 020 352	color: dark
Maurice Mary	17/10/2010	4	na	173,9158	953 919	color: blue
Julien Pottier	08/01/1992	1	na	171,4829	947 176	color: blue
Manon Martins	14/11/2034	3	60,24966	166,1542	768 406	color: dark
Corinne Lagarde	14/07/2001	1	62,26390	166,6074	933 124	color: dark
Roger Herve	03/04/2034	3	55,26330	171,1192	588 677	color: dark
Benjamin Lamy-Ferreira	28/05/1992	4	89,24445	177,5398	893 714	color: dark
Alexandrie Gosselin	23/11/2042	3	73,94103	174,9846	968 050	color: green
Luc Rodriguéz d'Dumas	22/11/1997	1	79,94190	170,5821	708 757	color: dark

Keep in mind that by setting the default display values, these calls can be avoided in most cases. They can be updated with function set_flextable_defaults().

old_settings <- set_flextable_defaults(
  digits = 1, decimal.mark = ",", big.mark = " ",
  na_str = "na", fmt_date = "%d/%m/%Y")

flextable(people)

name	birthday	n_children	weight	height	n_peanuts	eye_color
Susan Marié-David	18/05/2006	4	88,53768	162,6927	571 239	blue
Valentine Lemonnier	29/01/2040	1	na	171,4610	1 020 352	dark
Maurice Mary	17/10/2010	4	na	173,9158	953 919	blue
Julien Pottier	08/01/1992	1	na	171,4829	947 176	blue
Manon Martins	14/11/2034	3	60,24966	166,1542	768 406	dark
Corinne Lagarde	14/07/2001	1	62,26390	166,6074	933 124	dark
Roger Herve	03/04/2034	3	55,26330	171,1192	588 677	dark
Benjamin Lamy-Ferreira	28/05/1992	4	89,24445	177,5398	893 714	dark
Alexandrie Gosselin	23/11/2042	3	73,94103	174,9846	968 050	green
Luc Rodriguéz d'Dumas	22/11/1997	1	79,94190	170,5821	708 757	dark

do.call(set_flextable_defaults, old_settings)

8.3 Replace displayed labels

The function labelizor() replaces text values in a flextable with labels. The labels are defined with character named vector or with a function that transform the existing text.

Let’s illustrate this two options with a table representing an aggregation.

library(palmerpenguins)

ft_pen <- penguins |> 
  select(species, island, ends_with("mm")) |> 
  group_by(species, island) |> 
  summarise(
    across(
      where(is.numeric), 
      .fns = list(
        avg = ~ mean(.x, na.rm = TRUE),
        sd = ~ sd(.x, na.rm = TRUE)
      )
    ),
    .groups = "drop") |> 
  rename_with(~ tolower(gsub("_mm_", "_", .x, fixed = TRUE))) |> 
  flextable() |> 
  colformat_double() |>
  separate_header() |> 
  theme_vanilla() |> 
  align(align = "center", part = "all") |>
  valign(valign = "center", part = "header") |> 
  autofit()
ft_pen

species	island	bill				flipper
		length		depth		length
		avg	sd	avg	sd	avg	sd
Adelie	Biscoe	38.98	2.48	18.37	1.19	188.80	6.73
Adelie	Dream	38.50	2.47	18.25	1.13	189.73	6.59
Adelie	Torgersen	38.95	3.03	18.43	1.34	191.20	6.23
Chinstrap	Dream	48.83	3.34	18.42	1.14	195.82	7.13
Gentoo	Biscoe	47.50	3.08	14.98	0.98	217.19	6.48

Now, let’s replace the names of calculated columns by some labels:

ft_pen <- labelizor(
  x = ft_pen, 
  part = "header", 
  labels = c("avg" = "Mean", "sd" = "Standard Deviation"))
ft_pen

species	island	bill				flipper
		length		depth		length
		Mean	Standard Deviation	Mean	Standard Deviation	Mean	Standard Deviation
Adelie	Biscoe	38.98	2.48	18.37	1.19	188.80	6.73
Adelie	Dream	38.50	2.47	18.25	1.13	189.73	6.59
Adelie	Torgersen	38.95	3.03	18.43	1.34	191.20	6.23
Chinstrap	Dream	48.83	3.34	18.42	1.14	195.82	7.13
Gentoo	Biscoe	47.50	3.08	14.98	0.98	217.19	6.48

And now, let’s format headers with title case:

ft_pen <- labelizor(
  x = ft_pen, 
  part = "header", 
  labels = stringr::str_to_title)
ft_pen

Species	Island	Bill				Flipper
		Length		Depth		Length
		Mean	Standard Deviation	Mean	Standard Deviation	Mean	Standard Deviation
Adelie	Biscoe	38.98	2.48	18.37	1.19	188.80	6.73
Adelie	Dream	38.50	2.47	18.25	1.13	189.73	6.59
Adelie	Torgersen	38.95	3.03	18.43	1.34	191.20	6.23
Chinstrap	Dream	48.83	3.34	18.42	1.14	195.82	7.13
Gentoo	Biscoe	47.50	3.08	14.98	0.98	217.19	6.48

8.4 Multi content

User can also have more control over displayed content by using function compose/mk_par. The function enable to define the elements composing the paragraph and their respective formats. It can also be used to mix text chunks and images.

8.4.1 Function mk_par

flextable content can be defined with function mk_par().

It lets user control the formated content at the cell level of the table. It is possible to define a content for a row subset and a column as well as on the whole column. One can mix images and text (but not with PowerPoint because PowerPoint can not do it).

The function requires a call to as_paragraph() which will concatenate text or images chunks as a paragraph.

The following illustration is using dataset “fishes” (see table 15.3). It shows how to control the format of displayed values and how to associate them with specific text formatting properties:

ft <- flextable(fishes) %>% 
  mk_par(j = "latin_name", 
          value = as_paragraph(
            as_chunk(latin_name, 
                     props = fp_text_default(color = "#C32900", bold = TRUE)))) %>% 
  mk_par(j = "french_name", 
          value = as_paragraph(
            as_chunk(french_name, 
                     props = fp_text_default(color = "#006699", bold = TRUE))))
ft

latin_name	french_name	X00	X01
Acipenser Sturio	(L. 1758) Esturgeon européen
Alosa alosa	(L.1758) Alose vraie	+	+
Alosa fallax	(Lac. 1803) Alose feinte	+	+
Anguilla anguilla	(L. 1758) Anguille	+	+
Lampetra fluviatilis	(L. 1758) Lamproie de rivière		+
Liza ramada	(Risso 1826) Mulet porc	+	+

With that system, it’s easy to concatenate multiple values:

ft <- flextable(fishes, col_keys = c("dummy", "X00", "X01")) %>%
  mk_par(j = "dummy", value = as_paragraph(as_i(latin_name), as_b(french_name))) %>% 
  color(j = "dummy", color = "#006699") %>% 
  set_header_labels(dummy = "Species")
ft

Species	X00	X01
Acipenser Sturio (L. 1758) Esturgeon européen
Alosa alosa (L.1758) Alose vraie	+	+
Alosa fallax (Lac. 1803) Alose feinte	+	+
Anguilla anguilla (L. 1758) Anguille	+	+
Lampetra fluviatilis (L. 1758) Lamproie de rivière		+
Liza ramada (Risso 1826) Mulet porc	+	+

Or to define specific title headers:

mk_par( 
  ft, j = "dummy", part = "header",
  value = as_paragraph(
    "Species ", 
    as_chunk("* latin/french name", 
             props = fp_text_default(color = "#006699", vertical.align = "superscript"))
    )
  )

Species * latin/french name	X00	X01
Acipenser Sturio (L. 1758) Esturgeon européen
Alosa alosa (L.1758) Alose vraie	+	+
Alosa fallax (Lac. 1803) Alose feinte	+	+
Anguilla anguilla (L. 1758) Anguille	+	+
Lampetra fluviatilis (L. 1758) Lamproie de rivière		+
Liza ramada (Risso 1826) Mulet porc	+	+

Note that mk_par is not appending but is replacing the content.

8.4.2 Sugar functions for complex formatting

Functions as_b, as_i, as_sub, as_sup are special functions that can be used together. They set a value as bold, italic, subscripted or superscripted. This is particularly useful when the headers need complex formatting.

data <- structure(list(Species = structure(1:3, .Label = c("setosa", 
"versicolor", "virginica"), class = "factor"), col1 = c(5.006, 
5.936, 6.588)), class = "data.frame", row.names = c(NA, -3L))

ft <- flextable(data) %>%
  mk_par(
    part = "header", j = "Species",
    value = as_paragraph(as_i(as_b("Species")))
  ) %>%
  mk_par(
    part = "header", j = "col1",
    value = as_paragraph(as_b("µ"), as_sup("blah"))
  )
ft

Species	µblah
setosa	5.006
versicolor	5.936
virginica	6.588

8.4.3 Append or prepend content

prepend_chunks() or append_chunks() functions are handy functions that let users add in an existing paragraph one or more chunks. It can be any function dedicated to chunk creation, i.e. as_image(), as_chunk(), as_equation(), gg_chunk(), plot_chunk(). Function prepend_chunks() can be used to add tabulations for example.

ft <- flextable(data) %>%
  append_chunks(
    part = "body", i = 1, j = "Species",
    as_b(" some bold text")
  ) %>%
  prepend_chunks(
    part = "body", j = "col1", i = 2,
    as_chunk("hello ", props = fp_text_default(color = "red"))
  )
ft

Species	col1
setosa some bold text	5.006
versicolor	hello 5.936
virginica	6.588

8.5 Images

Function mk_par supports images insertion. Use function as_image in as_paragraph call.

The following illustration is using dataset “Tennis players” (see table 15.1).

To display only one image per cell, you can use the colformat_image function. The dimensions of the image(s) must always be specified.

flextable(tennis_players) %>%
  colformat_image(j = "head", width = .5, height = 0.5) %>% 
  colformat_image(j = "flag", width = .5, height = 0.33)

Rank	Player	Percentage	Games.Won	Total.Games	Matches
1	Roger Federer	92.63	2 739	2 957	205
2	Lleyton Hewitt	85.29	1 740	2 040	149
3	Feliciano Lopez	89.86	1 684	1 874	122
4	Ivo Karlovic	94.87	1 645	1 734	113
5	Andy Murray	88.89	1 528	1 719	121
6	Pete Sampras	92.66	1 478	1 595	105
7	Greg Rusedski	90.33	1 476	1 634	116
8	Tim Henman	83.77	1 461	1 744	110
9	Novak Djokovic	89.12	1 442	1 618	106
10	Andy Roddick	92.76	1 410	1 520	103

For a more complex display, such as mixing text and image, use the mk_par and as_image functions.

flextable(tennis_players,
  col_keys = c(
    "Rank", "Player", "Percentage",
    "Games.Won", "Total.Games", "Matches"
  )
) %>%
  mk_par(
    j = "Player",
    value = as_paragraph(
      as_image(src = head, width = .5, height = 0.5),
      " ",
      as_image(src = flag, width = .5, height = 0.33),
      " ", as_chunk(x = Player, fp_text_default(color = "#337ab7"))
    )
  )

Rank	Player	Percentage	Games.Won	Total.Games	Matches
1	Roger Federer	92.63	2 739	2 957	205
2	Lleyton Hewitt	85.29	1 740	2 040	149
3	Feliciano Lopez	89.86	1 684	1 874	122
4	Ivo Karlovic	94.87	1 645	1 734	113
5	Andy Murray	88.89	1 528	1 719	121
6	Pete Sampras	92.66	1 478	1 595	105
7	Greg Rusedski	90.33	1 476	1 634	116
8	Tim Henman	83.77	1 461	1 744	110
9	Novak Djokovic	89.12	1 442	1 618	106
10	Andy Roddick	92.76	1 410	1 520	103

8.6 Images and limitation for PowerPoint

Using images in flextable is not supported when output format is PowerPoint. This is not a choice nor a unimplemented feature. This is because PowerPoint is not able to embed images in a table cell. That’s a PowerPoint limitation. The same limitation occurs with ggplot charts and mini charts.

If beeing able to display images in PowerPoint table is important to you, you can use the plot function or the save_as_image and embed the result in the PowerPoint. You will of course loose ability to edit the table in PowerPoint.

8.7 Mini charts

set_flextable_defaults(
  post_process_html = function(x){
    theme_alafoli(x) %>% 
      align(align = "center", part = "all") %>% 
      align(align = "left", part = "footer") %>% 
      autofit()
  }
)

8.7.1 base plots and ggplot objects

You can insert mini plots, four types are available: ‘box’, ‘line’, ‘points’ and ‘density’. This requires to store a list column in your data.frame as these are functions that need more than a single point.

z <- as.data.table(iris)
z <- z[, list(
  data = list(.SD$Sepal.Length)
), by = "Species"]

flextable(z) %>% 
  mk_par(j = "data", value = as_paragraph(
    plot_chunk(value = data, type = "dens", col = "red")
    ))

Species	data
setosa
versicolor
virginica

ggplot objects are also supported by using gg_chunk(). It let users implement any graphics with ggplot2.

It usually requires a structure containing data grouped by one or more factors and a function to call on each content that produces a ggplot graph (in which adding the theme_void() is common).

Below the function - it will draw bars:

gg_bars <- function(z) {
  z <- scale(z)
  z <- na.omit(z)
  z <- data.frame(x = seq_along(z), z = z, w = z < 0)
  ggplot(z, aes(x = x, y = z, fill = w)) +
    geom_col(show.legend = FALSE) +
    theme_void()
}

Now the dataset:

dat <- as.data.table(mtcars)
z <- dat[,
  lapply(.SD, function(x) list(gg_bars(x))),
  by = c("vs", "am"), .SDcols = c("mpg", "disp", "drat")
]

And now the flextable with the ggplots:

ft <- flextable(z)
ft <- mk_par(ft, 
    j = c("mpg", "disp", "drat"),
    value = as_paragraph(gg_chunk(value = ., height = .15, width = 1)),
    use_dot = TRUE
  )
ft

vs	am	mpg	disp	drat
0	1
1	1
1	0
0	0

8.7.2 minibar

Function mk_par supports mini barplots insertion. Use function minibar in as_paragraph call:

flextable( head(iris, n = 10 )) %>% 
  mk_par(j = 1,
          value = as_paragraph(
            minibar(value = Sepal.Length, max = max(Sepal.Length), height = .15)
            ),
  part = "body")

Sepal.Width	Petal.Length	Petal.Width	Species
3.5	1.4	0.2	setosa
3.0	1.4	0.2	setosa
3.2	1.3	0.2	setosa
3.1	1.5	0.2	setosa
3.6	1.4	0.2	setosa
3.9	1.7	0.4	setosa
3.4	1.4	0.3	setosa
3.4	1.5	0.2	setosa
2.9	1.4	0.2	setosa
3.1	1.5	0.1	setosa

8.7.3 linerange

Function mk_par supports mini linerange insertion. Use function linerange in as_paragraph call:

flextable( head(iris, n = 10 )) %>% 
  mk_par(j = 1,
          value = as_paragraph(
            linerange(value = Sepal.Length, max = max(Sepal.Length), height = .15)
            ),
  part = "body")

Sepal.Width	Petal.Length	Petal.Width	Species
3.5	1.4	0.2	setosa
3.0	1.4	0.2	setosa
3.2	1.3	0.2	setosa
3.1	1.5	0.2	setosa
3.6	1.4	0.2	setosa
3.9	1.7	0.4	setosa
3.4	1.4	0.3	setosa
3.4	1.5	0.2	setosa
2.9	1.4	0.2	setosa
3.1	1.5	0.1	setosa