Intro

If you plan to use kableExtra in a non-bootstrap HTML theme, feel free to do so. The only part that will be impacted is the bootstrap_options in kable_styling (that’s why it’s named in this way). This document shows the look of tables in prettydoc (by yixuan).

Getting Started

Here we are using the first few columns and rows from dataset mtcars

library(knitr)
library(kableExtra)
dt <- mtcars[1:5, 1:6]

When you are using kable(), if you don’t specify format, by default it will generate a markdown table and let pandoc handle the conversion from markdown to HTML/PDF. This is the most favorable approach to render most simple tables as it is format independent. If you switch from HTML to pdf, you basically don’t need to change anything in your code. However, markdown doesn’t support complex table. For example, if you want to have a double-row header table, markdown just cannot provide you the functionality you need. As a result, when you have such a need, you should define format in kable() as either “html” or “latex”. You can also define a global option at the beginning using options(knitr.table.format = "html") so you don’t repeat the step everytime.

options(knitr.table.format = "html") 
## If you don't define format here, you'll need put `format = "html"` in every kable function.

kable(dt)

kable(dt) %>%
  kable_styling(full_width = F)

kable(dt) %>%
  kable_styling(full_width = F, position = "left")

kable(dt) %>%
  kable_styling(full_width = F, position = "float_right")

kable(dt) %>%
  kable_styling(font_size = 7)

Add Extra Header Rows

Tables with multi-row headers can be very useful to demonstrate grouped data. To do that, you can pipe your kable object into add_header_above(). The header variable is supposed to be a named character with the names as new column names and values as column span. For your convenience, if column span equals to 1, you can ignore the =1 part so the function below can be written as `add_header_above(c(" “,”Group 1" = 2, “Group 2” = 2, “Group 3” = 2)).

kable(dt) %>%
  kable_styling("striped") %>%
  add_header_above(c(" " = 1, "Group 1" = 2, "Group 2" = 2, "Group 3" = 2))

In fact, if you want to add another row of header on top, please feel free to do so.

kable(dt) %>%
  kable_styling(c("striped", "bordered")) %>%
  add_header_above(c(" ", "Group 1" = 2, "Group 2" = 2, "Group 3" = 2)) %>%
  add_header_above(c(" ", "Group 4" = 4, "Group 5" = 2)) %>%
  add_header_above(c(" ", "Group 6" = 6))

Add footnote

kable(dt) %>%
  kable_styling("striped") %>%
  add_footnote(c("Footnote 1", "Have a good day."), notation = "alphabet")

kable(dt) %>%
  kable_styling("striped") %>%
  add_footnote(c("Footnote 1", "Have a good day."), notation = "number")

kable(dt) %>%
  kable_styling("striped") %>%
  add_footnote(c("Footnote 1", "Footnote 2", "Footnote 3"), notation = "symbol")

kable(dt, caption = "Demo Table[note]") %>%
  kable_styling("striped") %>%
  add_header_above(c(" ", "Group 1[note]" = 3, "Group 2[note]" = 3)) %>%
  add_footnote(c("This table is from mtcars", 
                 "Group 1 contains mpg, cyl and disp", 
                 "Group 2 contains hp, drat and wt"), 
               notation = "symbol")

Group Rows

Sometimes we want a few rows of the table being grouped together. They might be items under the same topic (e.g., animals in one species) or just different data groups for a categorical variable (e.g., age < 40, age > 40). With the new function pack_rows() in kableExtra, this kind of task can be completed in one line. Please see the example below. Note that when you count for the start/end rows of the group, you don’t need to count for the header rows nor other group label rows. You only need to think about the row numbers in the “original R dataframe”.

kable(mtcars[1:10, 1:6], caption = "Group Rows") %>%
  kable_styling("striped", full_width = F) %>%
  pack_rows("Group 1", 4, 7) %>%
  pack_rows("Group 2", 8, 10)

For advanced users, you can even define your own css for the group labeling.

kable(dt) %>%
  kable_styling("striped", full_width = F) %>%
  pack_rows("Group 1", 3, 5, label_row_css = "background-color: #666; color: #fff;")

Add indentation

Unlike pack_rows(), which will insert a labeling row, sometimes we want to list a few sub groups under a total one. In that case, add_indent() is probably more apporiate. For advanced users, you can even define your own css for the group labeling.

kable(dt) %>%
  kable_styling("striped", full_width = F) %>%
  add_indent(c(1, 3, 5))

The following feature is introduced in kableExtra 0.2.1.

Column Style Specification

When you have a table with lots of explanatory texts, you may want to specified the column width for different column, since the auto adjust in HTML may not work in its best way while basic LaTeX table is really bad at handling text wrapping. Also, sometimes, you may want to highlight a column (e.g. a “Total” column) by making it bold. In these scenario, you can use column_spec(). You can find an example below.

text_tbl <- data.frame(
  Items = c("Item 1", "Item 2", "Item 3"),
  Features = c(
    "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin vehicula tempor ex. Morbi malesuada sagittis turpis, at venenatis nisl luctus a. ",
    "In eu urna at magna luctus rhoncus quis in nisl. Fusce in velit varius, posuere risus et, cursus augue. Duis eleifend aliquam ante, a aliquet ex tincidunt in. ", 
    "Vivamus venenatis egestas eros ut tempus. Vivamus id est nisi. Aliquam molestie erat et sollicitudin venenatis. In ac lacus at velit scelerisque mattis. "
  )
)

kable(text_tbl) %>%
  kable_styling(full_width = F) %>%
  column_spec(1, bold = T) %>%
  column_spec(2, width = "30em")