flextable layout

flextable layout can be easily managed. A set of functions will let you merge cells, add title rows, add footer notes, change the withs or heights.

flextable col_keys

Parameter col_keys of function flextable define the variables to display and their order.

data <- iris[c(1:3, 51:53, 101:104),]
myft <- flextable(data, col_keys = c("Species", "Sepal.Length", "Petal.Length") )
myft

Species	Sepal.Length	Petal.Length
setosa	5.100	1.400
setosa	4.900	1.400
setosa	4.700	1.300
versicolor	7.000	4.700
versicolor	6.400	4.500
versicolor	6.900	4.900
virginica	6.300	6.000
virginica	5.800	5.100
virginica	7.100	5.900
virginica	6.300	5.600

If parameter col_keys has variables that are not existing in the dataset, they will be considered as blank columns and can be used as separators (in fact they can be use as you want, there is only no mapping of data associated).

myft <- flextable(
  data = data, 
  col_keys = c("Species", "col_1", "Sepal.Length", "Petal.Length") )
myft <- theme_vanilla(myft)
myft <- autofit(myft)
myft <- empty_blanks(myft)
myft

Species	Sepal.Length	Petal.Length
setosa	5.100	1.400
setosa	4.900	1.400
setosa	4.700	1.300
versicolor	7.000	4.700
versicolor	6.400	4.500
versicolor	6.900	4.900
virginica	6.300	6.000
virginica	5.800	5.100
virginica	7.100	5.900
virginica	6.300	5.600

col_keys default values are the names of the data.frame used to fill the flextable.

Change labels

Use set_header_labels() to replace labels of the bottom row of header. When the flextable is created, their values are the column names of the data.frame.

ft <- flextable( head( iris ) ) 
ft <- set_header_labels(ft, Sepal.Length = "Sepal length", 
    Sepal.Width = "Sepal width", Petal.Length = "Petal length",
    Petal.Width = "Petal width" )
ft

Sepal length	Sepal width	Petal length	Petal width	Species
5.100	3.500	1.400	0.200	setosa
4.900	3.000	1.400	0.200	setosa
4.700	3.200	1.300	0.200	setosa
4.600	3.100	1.500	0.200	setosa
5.000	3.600	1.400	0.200	setosa
5.400	3.900	1.700	0.400	setosa

New header rows can be added at the top or bottom of the header. This part in documented in part Manage headers and footers.

Under the hood, the names are in a single row data.frame associated with the header part of the flextable. You can add new rows later, they will be binded to that data.frame.

Cell merging

To illustrate functions, we will use a basic flextable example:


dat <- data.frame(
  letters1 = c("a", "b", "b", "c"), 
  letters2 = c("d", "e", "b", "b"), 
  number = 1:4, stringsAsFactors = FALSE )

myft <- flextable(dat)
myft <- theme_box(myft)
myft

letters1	letters2	number
a	d	1
b	e	2
b	b	3
c	b	4

vertical merging of similar values

merge_v() will merge adjacent duplicated cells for each column of the selection.

merge_v(myft, j = ~ letters1 + letters2 )

letters1	letters2	number
a	d	1
b	e	2
b	b	3
c	b	4

horizontal merging of similar values

merge_h() will merge adjacent duplicated cells for each row of the selection.

merge_h(myft)

letters1	letters2	number
a	d	1
b	e	2
b		3
c	b	4

horizontal merging of columns

Function merge_h_range is close to the previous one but merge all colums between a range of columns.

merge_h_range(myft, 
  i =  ~ number < 3, 
  j1 = "letters1", j2 = "letters2")

letters1	letters2	number
a		1
b		2
b	b	3
c	b	4

general merging function

merge_at() will merge cells for a given continuous selection of rows and cells. The result is a single cell.

myft %>% 
  merge_at(
    i = 1:2, j = 1:2)

letters1	letters2	number
a		1
a		2
b	b	3
c	b	4

delete merging informations

If you want to get rid of all merging (i.e. for development purposes), use merge_none():

merge_none(myft)

letters1	letters2	number
a	d	1
b	e	2
b	b	3
c	b	4

Borders and merging

When cells are merged, the rendered borders will be those of the first cell. If a column is made of three merged cells, the bottom border that will be seen will be the bottom border of the first cell in the column. From a user point of view, this is wrong, the bottom should be the one defined for cell 3. Function fix_border_issues is trying to fix that issue.

ft <- data.frame(a = 1:5, b = 6:10) %>%
  flextable() %>% theme_box() %>%
  merge_at(i = 4:5, j = 1, part = "body") %>%
  hline(i = 5, part = "body",
        border = fp_border(color = "orange", width = 3) )
ft

a	b
1	6
2	7
3	8
4	9
4	10

fix_border_issues(ft)

a	b
1	6
2	7
3	8
4	9
4	10

Manage headers and footers

Use one of the following functions to add an header row or a footer row:

add_footer
add_footer_lines
add_footer_row
add_header
add_header_lines
add_header_row

We will mainly demonstrate headers but same can be apply with footers.

ft <- flextable( head( iris ) ) 
ft <- set_header_labels(ft, Sepal.Length = "Sepal", 
    Sepal.Width = "Sepal", Petal.Length = "Petal",
    Petal.Width = "Petal" )
ft

Sepal	Sepal	Petal	Petal	Species
5.100	3.500	1.400	0.200	setosa
4.900	3.000	1.400	0.200	setosa
4.700	3.200	1.300	0.200	setosa
4.600	3.100	1.500	0.200	setosa
5.000	3.600	1.400	0.200	setosa
5.400	3.900	1.700	0.400	setosa

add a row of labels

ft <- add_header(ft, 
  Sepal.Length = "length", 
  Sepal.Width = "width", 
  Petal.Length = "length", 
  Petal.Width = "width", 
  top = FALSE )
ft <- theme_booktabs(ft)

Sepal	Sepal	Petal	Petal	Species
length	width	length	width
5.100	3.500	1.400	0.200	setosa
4.900	3.000	1.400	0.200	setosa
4.700	3.200	1.300	0.200	setosa
4.600	3.100	1.500	0.200	setosa
5.000	3.600	1.400	0.200	setosa
5.400	3.900	1.700	0.400	setosa

lines of text

ft <- add_header_lines(ft, 
  values = c("this is a first line", 
     "this is a second line") ) 
ft <- theme_booktabs(ft)

this is a second line
this is a first line
Sepal	Sepal	Petal	Petal	Species
length	width	length	width
5.100	3.500	1.400	0.200	setosa
4.900	3.000	1.400	0.200	setosa
4.700	3.200	1.300	0.200	setosa
4.600	3.100	1.500	0.200	setosa
5.000	3.600	1.400	0.200	setosa
5.400	3.900	1.700	0.400	setosa

Define headers with a reference table

Use set_header_df() with a data.frame as parameter. Columns of the dataset will be transposed and joined using a key column.

The reference table

Variable col_keys define key values to match with flextable column keys (defined by argument col_keys of flextable() function).

This key column will not be displayed. Other variables will added as rows. Note that variables names are not displayed.

typology <- data.frame(
  col_keys = c( "Sepal.Length", 
    "Sepal.Width", "Petal.Length",
    "Petal.Width", "Species" ),
  type = c("double", "double", "double", 
    "double", "factor"),
  what = c("Sepal", "Sepal", "Petal", 
    "Petal", "Species"),
  measure = c("Length", "Width", "Length", 
    "Width", "Species"),
  stringsAsFactors = FALSE )

col_keys	type	what	measure
Sepal.Length	double	Sepal	Length
Sepal.Width	double	Sepal	Width
Petal.Length	double	Petal	Length
Petal.Width	double	Petal	Width
Species	factor	Species	Species

Use it as header rows

Then use set_header_df() with parameter key. key is the name of the column used to permform the join operation.

Order of columns matters, first column will be first row, second one will be the second row, etc.

ft <- flextable( head( iris ) )
ft <- set_header_df( ft, mapping = typology, key = "col_keys" )

ft <- merge_h(ft, part = "header")
ft <- merge_v(ft, part = "header")

ft <- theme_booktabs(ft)
ft <- autofit(ft)
ft <- fix_border_issues(ft)

double				factor
Sepal		Petal		Species
Length	Width	Length	Width	Species
5.100	3.500	1.400	0.200	setosa
4.900	3.000	1.400	0.200	setosa
4.700	3.200	1.300	0.200	setosa
4.600	3.100	1.500	0.200	setosa
5.000	3.600	1.400	0.200	setosa
5.400	3.900	1.700	0.400	setosa

Cell widths and heights

The default sizes of flextable columns and rows are set by default values. This will drive to inadequate rows heights and columns widths in some cases. You can use function dim to get flextable dimensions.

ft_base <- flextable(head(mtcars))
ft_base <- theme_vader(ft_base, fontsize = 13)
ft_base

mpg	cyl	disp	hp	drat	wt	qsec	vs	am	gear	carb
21.000	6.000	160.000	110.000	3.900	2.620	16.460	0.000	1.000	4.000	4.000
21.000	6.000	160.000	110.000	3.900	2.875	17.020	0.000	1.000	4.000	4.000
22.800	4.000	108.000	93.000	3.850	2.320	18.610	1.000	1.000	4.000	1.000
21.400	6.000	258.000	110.000	3.080	3.215	19.440	1.000	0.000	3.000	1.000
18.700	8.000	360.000	175.000	3.150	3.440	17.020	0.000	0.000	3.000	2.000
18.100	6.000	225.000	105.000	2.760	3.460	20.220	1.000	0.000	3.000	1.000

dim(ft_base)
#> $widths
#>  mpg  cyl disp   hp drat   wt qsec   vs   am gear carb 
#> 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 
#> 
#> $heights
#> [1] 0.25 0.25 0.25 0.25 0.25 0.25 0.25

Pretty dimensions

Function dim_pretty() is computing optimized widths and heights.

dim_pretty(ft_base)
#> $widths
#>  [1] 0.7116790 0.6090585 0.8142994 0.8142994 0.6090585 0.6090585 0.7116790
#>  [8] 0.6090585 0.6090585 0.6090585 0.6090585
#> 
#> $heights
#> [1] 0.3220916 0.2800383 0.2800383 0.2800383 0.2800383 0.2800383 0.2800383

Adjusts automatically cell widths and heights

Function autofit() optimises widths and heights of the flextable. This function is almost always to be called once when using flextable objects, it makes compact tables.

ft <- autofit(ft_base, add_w = 0, add_h = 0)

dim(ft)
#> $widths
#>       mpg       cyl      disp        hp      drat        wt      qsec 
#> 0.7116790 0.6090585 0.8142994 0.8142994 0.6090585 0.6090585 0.7116790 
#>        vs        am      gear      carb 
#> 0.6090585 0.6090585 0.6090585 0.6090585 
#> 
#> $heights
#> [1] 0.3220916 0.2800383 0.2800383 0.2800383 0.2800383 0.2800383 0.2800383
ft

mpg	cyl	disp	hp	drat	wt	qsec	vs	am	gear	carb
21.000	6.000	160.000	110.000	3.900	2.620	16.460	0.000	1.000	4.000	4.000
21.000	6.000	160.000	110.000	3.900	2.875	17.020	0.000	1.000	4.000	4.000
22.800	4.000	108.000	93.000	3.850	2.320	18.610	1.000	1.000	4.000	1.000
21.400	6.000	258.000	110.000	3.080	3.215	19.440	1.000	0.000	3.000	1.000
18.700	8.000	360.000	175.000	3.150	3.440	17.020	0.000	0.000	3.000	2.000
18.100	6.000	225.000	105.000	2.760	3.460	20.220	1.000	0.000	3.000	1.000

Soft returns (a line break in a paragraph) support : function autofit and dim_pretty do not support soft returns and may return wrong results (will be considered as "").

Adjusts manually cell widths and heights

Function width() and height() let you control dimensions of a flextable. height_all() is an helper function to set the same height to each part of the table.

ft <- autofit(ft_base)
ft <- width(ft, j = ~ mpg + cyl + disp, width = 2)
ft <- height_all( ft, height = .4 )
ft <- height( ft, i = 3, height = 1 )
ft

mpg	cyl	disp	hp	drat	wt	qsec	vs	am	gear	carb
21.000	6.000	160.000	110.000	3.900	2.620	16.460	0.000	1.000	4.000	4.000
21.000	6.000	160.000	110.000	3.900	2.875	17.020	0.000	1.000	4.000	4.000
22.800	4.000	108.000	93.000	3.850	2.320	18.610	1.000	1.000	4.000	1.000
21.400	6.000	258.000	110.000	3.080	3.215	19.440	1.000	0.000	3.000	1.000
18.700	8.000	360.000	175.000	3.150	3.440	17.020	0.000	0.000	3.000	2.000
18.100	6.000	225.000	105.000	2.760	3.460	20.220	1.000	0.000	3.000	1.000

Groups as row titles

Package flextable does not support data transformation. A grouped dataset is then needed (and tidy). This has to be done prior to the creation of the object.

Function as_grouped_data will modify data structure so that it will be easy to manage grouped data representation. Repeated consecutive values of group columns will be used to define the title of the groups and will be added as a row title.

Let’s have an example with aggragated data from dataset CO2:

library(data.table)
data_CO2 <- dcast(as.data.table(CO2), 
  Treatment + conc ~ Type, value.var = "uptake", fun.aggregate = mean)
head(data_CO2)
#>     Treatment conc   Quebec Mississippi
#> 1: nonchilled   95 15.26667    11.30000
#> 2: nonchilled  175 30.03333    20.20000
#> 3: nonchilled  250 37.40000    27.53333
#> 4: nonchilled  350 40.36667    29.90000
#> 5: nonchilled  500 39.60000    30.60000
#> 6: nonchilled  675 41.50000    30.53333

as_grouped_data will restructure the dataset:

data_CO2 <- as_grouped_data(x = data_CO2, groups = c("Treatment"))
head(data_CO2)
#>    Treatment conc   Quebec Mississippi
#> 1 nonchilled   NA       NA          NA
#> 3       <NA>   95 15.26667    11.30000
#> 4       <NA>  175 30.03333    20.20000
#> 5       <NA>  250 37.40000    27.53333
#> 6       <NA>  350 40.36667    29.90000
#> 7       <NA>  500 39.60000    30.60000

The result is suitable for method as_flextable. A call to this function and few formatting operations are producing the following result:

zz <- as_flextable( data_CO2 ) %>% 
  bold(j = 1, i = ~ !is.na(Treatment), bold = TRUE, part = "body" ) %>% 
  bold(part = "header", bold = TRUE ) %>% 
  width(width = 1.5)
zz

conc	Quebec	Mississippi
Treatment: nonchilled
95.000	15.267	11.300
175.000	30.033	20.200
250.000	37.400	27.533
350.000	40.367	29.900
500.000	39.600	30.600
675.000	41.500	30.533
1000.000	43.167	31.600
Treatment: chilled
95.000	12.867	9.600
175.000	24.133	14.767
250.000	34.467	16.100
350.000	35.800	16.600
500.000	36.667	16.633
675.000	37.500	18.267
1000.000	40.833	18.733

It’s now easier to customize the rendering. Let’s format column conc as an integer column:

zz <- zz %>% 
  compose(i = ~ !is.na(conc), j = "conc", 
          value = as_paragraph(
            as_chunk(conc, formater = function(x) sprintf("%.0f", x))
          )
  )
zz

conc	Quebec	Mississippi
Treatment: nonchilled
95	15.267	11.300
175	30.033	20.200
250	37.400	27.533
350	40.367	29.900
500	39.600	30.600
675	41.500	30.533
1000	43.167	31.600
Treatment: chilled
95	12.867	9.600
175	24.133	14.767
250	34.467	16.100
350	35.800	16.600
500	36.667	16.633
675	37.500	18.267
1000	40.833	18.733

Now let’s add nice bars before displaying the figures:

zz <- zz %>% 
  compose(i = ~ is.na(Treatment), j = "Quebec", 
          value = as_paragraph(
            minibar(Quebec), 
            " ", 
            as_chunk(Quebec, formater = function(x) sprintf("%.01f", x))
            )
          ) %>% 
  compose(i = ~ is.na(Treatment), j = "Mississippi", 
          value = as_paragraph( minibar(Mississippi), 
                                " ",
                                as_chunk(Mississippi, 
                                         formater = function(x) sprintf("%.01f", x) )
                                )
          ) %>% 
  align(j = 2:3, align = "left")
zz

conc	Quebec	Mississippi
Treatment: nonchilled
95	15.3	11.3
175	30.0	20.2
250	37.4	27.5
350	40.4	29.9
500	39.6	30.6
675	41.5	30.5
1000	43.2	31.6
Treatment: chilled
95	12.9	9.6
175	24.1	14.8
250	34.5	16.1
350	35.8	16.6
500	36.7	16.6
675	37.5	18.3
1000	40.8	18.7

And finally, add a footnote in the footer part:

add_footer_lines(zz, "dataset CO2 has been used for this flextable")

conc	Quebec	Mississippi
Treatment: nonchilled
95	15.3	11.3
175	30.0	20.2
250	37.4	27.5
350	40.4	29.9
500	39.6	30.6
675	41.5	30.5
1000	43.2	31.6
Treatment: chilled
95	12.9	9.6
175	24.1	14.8
250	34.5	16.1
350	35.8	16.6
500	36.7	16.6
675	37.5	18.3
1000	40.8	18.7
dataset CO2 has been used for this flextable

xtable

xtable objects can be transformed as flextable objects with function xtable_to_flextable().

if( require("xtable") ){
  temp.ts <- ts(cumsum(1 + round(rnorm(100), 0)),
    start = c(1954, 7), frequency = 12)
  ft <- xtable_to_flextable(x = xtable(temp.ts, digits = 0),
    NA.string = "-")
  ft
}

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
1954							0.000	1.000	2.000	2.000	4.000	5.000
1955	8.000	9.000	9.000	9.000	10.000	12.000	14.000	15.000	19.000	22.000	22.000	23.000
1956	22.000	24.000	25.000	25.000	26.000	26.000	28.000	31.000	31.000	31.000	34.000	35.000
1957	39.000	40.000	43.000	42.000	43.000	44.000	44.000	45.000	46.000	46.000	46.000	47.000
1958	48.000	49.000	50.000	50.000	52.000	52.000	55.000	56.000	57.000	59.000	59.000	61.000
1959	62.000	63.000	64.000	64.000	65.000	67.000	69.000	71.000	72.000	73.000	73.000	74.000
1960	75.000	76.000	77.000	79.000	78.000	79.000	81.000	81.000	82.000	84.000	84.000	85.000
1961	86.000	88.000	90.000	92.000	93.000	96.000	96.000	95.000	96.000	96.000	98.000	100.000
1962	101.000	103.000	104.000	104.000	104.000	106.000	108.000	110.000	111.000	113.000