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.

First, we explain the use of the colformat_* functions and then we will see how to fill cells with richer contents (i.e. being able to mix images, text and hyperlinks) with the compose(as_paragraph()) functions. Function compose() also exists in the ‘purrr’ package which often causes issues. The identical function mk_par() has been created to avoid package conflict issues, i.e. flextable::mk_par() and flextable::compose() are the same exact functions. For clarity, only mk_par() is used 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 recommend changing your data so that it contains \n or \t. Instead we recommend using 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

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

Each accepts a prefix and suffix argument that can be used to add a currency symbol for example. Also they all have a na_str argument (default 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

Thibaut L'Raymond

27/11/2044

2

56,86068

164,5779

976 777

color: green

Maggie Ollivier

31/10/2001

4

na

171,9639

847 422

color: green

Jules Bértrand

31/12/2033

3

na

169,8698

575 057

color: green

Denise Guichard

28/12/2002

4

na

163,7198

634 526

color: green

Denise Leconte-Ferrand

25/10/2004

2

82,29277

165,3216

879 465

color: green

Danielle Perrier

08/11/2018

3

56,53538

169,0166

1 039 523

color: dark

Louis Sanchéz

17/01/2038

2

72,51948

170,7113

1 012 998

color: green

Tristan Blondel

23/01/2027

0

66,48858

167,7011

654 813

color: blue

Camille Guérin

09/01/1991

3

86,10102

173,0896

1 146 045

color: dark

Hugues Paul

10/05/2031

4

68,20352

166,3979

701 682

color: blue

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

Thibaut L'Raymond

27/11/2044

2

56,86068

164,5779

976 777

green

Maggie Ollivier

31/10/2001

4

na

171,9639

847 422

green

Jules Bértrand

31/12/2033

3

na

169,8698

575 057

green

Denise Guichard

28/12/2002

4

na

163,7198

634 526

green

Denise Leconte-Ferrand

25/10/2004

2

82,29277

165,3216

879 465

green

Danielle Perrier

08/11/2018

3

56,53538

169,0166

1 039 523

dark

Louis Sanchéz

17/01/2038

2

72,51948

170,7113

1 012 998

green

Tristan Blondel

23/01/2027

0

66,48858

167,7011

654 813

blue

Camille Guérin

09/01/1991

3

86,10102

173,0896

1 146 045

dark

Hugues Paul

10/05/2031

4

68,20352

166,3979

701 682

blue

 
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 transforms the existing text.

Let’s illustrate these 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 with prettier 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

The user can have more control over displayed content by using function compose() or mk_par() which are identical. The function enables the user 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 the user control the formatted content at the cell level of the table. It is possible to define content for a row subset and a column as well as for the whole column. One can mix images and text (but not with PowerPoint because PowerPoint cannot 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 this 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 image 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

head

flag

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 limitations of PowerPoint

Using images in flextable is not supported when the output format is PowerPoint. This is not a choice nor an 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 being able to display images in PowerPoint tables 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 lose the 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

There are four types of mini plots available that can be inserted into flextables: ‘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 supported and can be inserted with gg_chunk(). It lets 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 used to 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.Length

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.Length

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