flextable layout

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

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

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

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

merge_v(myft, j = ~ letters1 + letters2 )

merge_h(myft)

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

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

merge_none(myft)

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

fix_border_issues(ft)

Manage headers and footers

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

• Most needs will be statisfied with functions add_header_row and add_footer_row. These are row oriented functions to let you add a single row of labels (that can be displayed along one or more columns in the new row).
• Functions add_header and add_footer are columns oriented functions that will let you add several values (one for each new row) for a given column. If labels are stored in a data.frame, use functions set_header_df and set_footer_df.
• Functions add_footer_lines and add_header_lines are sugar functions and should be used to add labels on one single row where all columns are merged together.

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

The operation below is changing labels that will be displayed instead of the original values (the names of dataset).

ft <- flextable( head( iris ) ) 
ft <- set_header_labels(ft, Sepal.Length = "Sepal", 
    Sepal.Width = "Sepal", Petal.Length = "Petal",
    Petal.Width = "Petal" )
# merge them 
ft <- merge_at(ft, i = 1, j = 1:2, part = "header")
ft <- merge_at(ft, i = 1, j = 3:4, part = "header")
ft

Now let’s add new row of labels.

ft <- add_header_row(ft, 
  values = c("", "length", "width", "length", "width"), top = FALSE )
ft <- theme_box(ft)

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

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 )

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)

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

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

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

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

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

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

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

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

And finally, add a footnote in the footer part:

add_footer_lines(zz, "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
}