Basic HTML table

Basic HTML output of kable looks very crude. To the end, it’s just a plain HTML table without any love from css.

kable(dt)

Bootstrap theme

When used on a HTML table, kable_styling() will automatically apply twitter bootstrap theme to the table. Now it should looks the same as the original pandoc output (the one when you don’t specify format in kable()) but this time, you are controlling it.

dt %>%
  kable() %>%
  kable_styling()

Bootstrap table classes

If you are familiar with twitter bootstrap, you probably have already known its predefined classes, including striped, bordered, hover, condensed and responsive. If you are not familiar, no worries, you can take a look at their documentation site to get a sense of how they look like. All of these options are available here.

For example, to add striped lines (alternative row colors) to your table and you want to highlight the hovered row, you can simply type:

kable(dt) %>%
  kable_styling(bootstrap_options = c("striped", "hover"))

The option condensed can also be handy in many cases when you don’t want your table to be too large. It has slightly shorter row height.

kable(dt) %>%
  kable_styling(bootstrap_options = c("striped", "hover", "condensed"))

Tables with option responsive looks the same with others on a large screen. However, on a small screen like phone, they are horizontally scrollable. Please resize your window to see the result.

kable(dt) %>%
  kable_styling(bootstrap_options = c("striped", "hover", "condensed", "responsive"))

Full width?

By default, a bootstrap table takes 100% of the width. It is supposed to use together with its grid system to scale the table properly. However, when you are writing a rmarkdown document, you probably don’t want to write your own css/or grid. For some small tables with only few columns, a page wide table looks awful. To make it easier, you can specify whether you want the table to have full_width or not in kable_styling. By default, full_width is set to be TRUE for HTML tables (note that for LaTeX, the default is FALSE since I don’t want to change the “common” looks unless you specified it.)

kable(dt) %>%
  kable_styling(bootstrap_options = "striped", full_width = F)

Position

Table Position only matters when the table doesn’t have full_width. You can choose to align the table to center, left or right side of the page

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

Becides these three common options, you can also wrap text around the table using the float-left or float-right options.

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

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras sit amet mauris in ex ultricies elementum vel rutrum dolor. Phasellus tempor convallis dui, in hendrerit mauris placerat scelerisque. Maecenas a accumsan enim, a maximus velit. Pellentesque in risus eget est faucibus convallis nec at nulla. Phasellus nec lacinia justo. Morbi fermentum, orci id varius accumsan, nibh neque porttitor ipsum, consectetur luctus risus arcu ac ex. Aenean a luctus augue. Suspendisse et auctor nisl. Suspendisse cursus ultrices quam non vulputate. Phasellus et pharetra neque, vel feugiat erat. Sed feugiat elit at mauris commodo consequat. Sed congue lectus id mattis hendrerit. Mauris turpis nisl, congue eget velit sed, imperdiet convallis magna. Nam accumsan urna risus, non feugiat odio vehicula eget.

Font size

If one of your tables is huge and you want to use a smaller font size for that specific table, you can use the font_size option.

kable(dt) %>%
  kable_styling(bootstrap_options = "striped", font_size = 7)

Fixed Table Header Row

If you happened to have a very long table, you may consider to use this fixed_header option to fix the header row on top as your readers scroll. By default, the background is set to white. If you need a different color, you can set fixed_header = list(enabled = T, background = "red").

kable(mtcars[1:10, 1:5]) %>%
  kable_styling(fixed_thead = T)

Column spec

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.

Warning: If you have a super long table, you should be cautious when you use column_spec as the xml node modification takes time.

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, border_right = T) %>%
  column_spec(2, width = "30em", background = "yellow")

Row spec

Similar with column_spec, you can define specifications for rows. Currently, you can either bold or italiciz an entire row. Note that, similar with other row-related functions in kableExtra, for the position of the target row, you don’t need to count in header rows or the group labelling rows.

kable(dt) %>%
  kable_styling("striped", full_width = F) %>%
  column_spec(5:7, bold = T) %>%
  row_spec(3:5, bold = T, color = "white", background = "#D7261E")

Header Rows

One special case of row_spec is that you can specify the format of the header row via row_spec(row = 0, ...).

kable(dt) %>%
  kable_styling("striped", full_width = F) %>%
  row_spec(0, angle = -45)

Conditional logic

It is very easy to use cell_spec with conditional logic. Here is an example.

library(dplyr)
mtcars[1:10, 1:2] %>%
  mutate(
    car = row.names(.),
    mpg = cell_spec(mpg, "html", color = ifelse(mpg > 20, "red", "blue")),
    cyl = cell_spec(cyl, "html", color = "white", align = "c", angle = 45, 
                    background = factor(cyl, c(4, 6, 8), 
                                        c("#666666", "#999999", "#BBBBBB")))
  ) %>%
  select(car, mpg, cyl) %>%
  kable(format = "html", escape = F) %>%
  kable_styling("striped", full_width = F)

Visualize data with Viridis Color

This package also comes with a few helper functions, including spec_color, spec_font_size & spec_angle. These functions can rescale continuous variables to certain scales. For example, function spec_color would map a continuous variable to any viridis color palettes. It offers a very visually impactful representation in a tabular format.

iris[1:10, ] %>%
  mutate_if(is.numeric, function(x) {
    cell_spec(x, bold = T, 
              color = spec_color(x, end = 0.9),
              font_size = spec_font_size(x))
  }) %>%
  mutate(Species = cell_spec(
    Species, color = "white", bold = T,
    background = spec_color(1:10, end = 0.9, option = "A", direction = -1)
  )) %>%
  kable(escape = F, align = "c") %>%
  kable_styling(c("striped", "condensed"), full_width = F)

In the example above, I’m using the mutate functions from dplyr. You don’t have to use it. Base R solutions like iris$Species <- cell_spec(iris$Species, color = "red") also works.

Text Specification

If you check the results of cell_spec, you will find that this function does nothing more than wrapping the text with appropriate HTML/LaTeX formatting syntax. The result of this function is just a vector of character strings. As a result, when you are writing a rmarkdown document or write some text in shiny apps, if you need extra markups other than bold or italic, you may use this function to color, change font size or rotate your text.

An aliased function text_spec is also provided for a more literal writing experience. In HTML, there is no difference between these two functions.

sometext <- strsplit(paste0(
  "You can even try to make some crazy things like this paragraph. ", 
  "It may seem like a useless feature right now but it's so cool ",
  "and nobody can resist. ;)"
), " ")[[1]]
text_formatted <- paste(
  text_spec(sometext, color = spec_color(1:length(sometext), end = 0.9),
            font_size = spec_font_size(1:length(sometext), begin = 5, end = 20)),
  collapse = " ")

# To display the text, type `r text_formatted` outside of the chunk

You can even try to make some crazy things like this paragraph. It may seem like a useless feature right now but it’s so cool and nobody can resist. ;)

Tooltip

It’s very easy to add a tooltip to text via cell_spec. For example, text_spec("tooltip", color = "red", tooltip = "Hello World") will give you something like Hover over me (you need to wait for a few seconds before your browser renders it).

Note that the original browser-based tooltip is slow. If you want to have a faster response, you may want to initialize bootstrap’s tooltip by putting the following HTML code on the page.

<script>
$(document).ready(function(){
    $('[data-toggle="tooltip"]').tooltip(); 
});
</script>

In a rmarkdown document, you can just drop it outside of any R chunks. Unfortunately however, for rmarkdown pages with a floating TOC (like this page), you can’t use bootstrap tooltips because there is a conflict in namespace between Bootstrap and JQueryUI (tocify.js). As a result, I can’t provide a live demo here. If you want to have a tooltip together with a floating TOC, you should use popover which has a very similar effect.

Popover Message

The popover message looks very similar with tooltip but it can hold more contents. Unlike tooltip which can minimally work without you manually enable that module, you have to enable the popover module to get it work. The upper side is that there is no conflict between Bootstrap & JQueryUI this time, you can use it without any concern.

<script>
$(document).ready(function(){
    $('[data-toggle="popover"]').popover(); 
});
</script>

popover_dt <- data.frame(
  position = c("top", "bottom", "right", "left"),
  stringsAsFactors = FALSE
)
popover_dt$`Hover over these items` <- cell_spec(
  paste("Message on", popover_dt$position), # Cell texts
  popover = spec_popover(
    content = popover_dt$position,
    title = NULL,                           # title will add a Title Panel on top
    position = popover_dt$position
  ))
kable(popover_dt, escape = FALSE) %>%
  kable_styling("striped", full_width = FALSE)

Links

You can add links to text via text_spec("Google", link = "https://google.com"): Google. If you want your hover message to be more obvious, it might be a good idea to put a # (go back to the top of the page) or javascript:void(0) (literally do nothing) in the link option. text_spec("Hover on me", link = "javascript:void(0)", popover = "Hello"): Hover on me

Integration with formattable

You can combine the good parts from kableExtra & formattable together into one piece. Read more at http://haozhu233.github.io/kableExtra/use_kableExtra_with_formattable.html

library(formattable)
mtcars[1:5, 1:4] %>%
  mutate(
    car = row.names(.),
    mpg = color_tile("white", "orange")(mpg),
    cyl = cell_spec(cyl, angle = (1:5)*60, 
                    background = "red", color = "white", align = "center"),
    disp = ifelse(disp > 200,
                  cell_spec(disp, color = "red", bold = T),
                  cell_spec(disp, color = "green", italic = T)),
    hp = color_bar("lightgreen")(hp)
  ) %>%
  select(car, everything()) %>%
  kable(escape = F) %>%
  kable_styling("hover", full_width = F) %>%
  column_spec(5, width = "3cm") %>%
  add_header_above(c(" ", "Hello" = 2, "World" = 2))

Add header rows to group columns

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))

Group rows via labeling

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 function group_rows()/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)

Another way to use pack_rows is to provide an grouping index, similar with add_header_above(). This feature is only available in kableExtra > 0.5.2.

# Not evaluated. This example generates the same table as above.
kable(mtcars[1:10, 1:6], caption = "Group Rows") %>%
  kable_styling("striped", full_width = F) %>%
  pack_rows(index = c(" " = 3, "Group 1" = 4, "Group 2" = 3))

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;")

Important Note!

Note that dplyr 0.8.0+ introduced a group_rows function as well for a trivial feature. Therefore, I’m create this pack_rows function as an alias to the original group_rows. In the future, I recommend all kableExtra users to use pack_rows instead of group_rows to get rid of the NAMESPACE conflict.

Alternatively, for pre-existing codes, you have two ways to solve this. You can either load kableExtra after dplyr or tidyverse, or to use the conflicted package. Here is an example.

# Method 1
pack_rows() # instead of group_rows()

# Method 2
library(dplyr)
library(kableExtra)

# Method 3
conflicted::conflict_prefer("group_rows", "kableExtra", "dplyr")

Row 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))

Group rows via multi-row cell

Function pack_rows is great for showing simple structural information on rows but sometimes people may need to show structural information with multiple layers. When it happens, you may consider to use collapse_rows instead, which will put repeating cells in columns into multi-row cells. The vertical allignment of the cell is controlled by valign with default as “top”.

collapse_rows_dt <- data.frame(C1 = c(rep("a", 10), rep("b", 5)),
                 C2 = c(rep("c", 7), rep("d", 3), rep("c", 2), rep("d", 3)),
                 C3 = 1:15,
                 C4 = sample(c(0,1), 15, replace = TRUE))
kable(collapse_rows_dt, align = "c") %>%
  kable_styling(full_width = F) %>%
  column_spec(1, bold = T) %>%
  collapse_rows(columns = 1:2, valign = "top")

Scroll box

If you have a huge table and you don’t want to reduce the font size to unreadable, you may want to put your HTML table in a scroll box, of which users can pick the part they like to read. Note that scroll box isn’t printer friendly, so be aware of that when you use this feature.

When you use scroll_box, you can specify either height or width. When you specify height, you will get a vertically scrollable box and vice versa. If you specify both, you will get a two-way scrollable box.

kable(cbind(mtcars, mtcars)) %>%
  kable_styling() %>%
  scroll_box(width = "500px", height = "200px")

You can also specify width using a percentage.

kable(cbind(mtcars, mtcars)) %>%
  add_header_above(c("a" = 5, "b" = 18)) %>%
  kable_styling() %>%
  scroll_box(width = "100%", height = "200px")

Starting from version 1.1.0, if you have a fixed-height box, the header row is fixed

Save HTML table directly

If you need to save those HTML tables but you don’t want to generate them through rmarkdown, you can try to use the save_kable() function. You can choose whether to let those HTML files be self contained (default is yes). Self contained files packed CSS into the HTML file so they are quite large when there are many.

kable(mtcars) %>%
  kable_styling() %>%
  save_kable(file = "table1.html", self_contained = T)

tables

The latest version of tables comes with a toKable() function, which is compatiable with functions in kableExtra (>=0.9.0).

xtable

For xtable users, if you want to use kableExtra functions on that, check out this xtable2kable() function shipped with kableExtra 1.0.

# Not evaluating
xtable::xtable(mtcars[1:4, 1:4], caption = "Hello xtable") %>%
  xtable2kable() %>%
  column_spec(1, color = "red")