Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Generate Manual Table of Contents in (R)Markdown Documents
#' Render Table of Contents
#'
#' A simple function to extract headers from an RMarkdown or Markdown document
#' and build a table of contents. Returns a markdown list with links to the
#' headers using
#' [pandoc header identifiers](http://pandoc.org/MANUAL.html#header-identifiers).
#'
#' WARNING: This function only works with hash-tag headers.
#'
#' Because this function returns only the markdown list, the header for the
#' Table of Contents itself must be manually included in the text. Use
#' `toc_header_name` to exclude the table of contents header from the TOC, or
#' set to `NULL` for it to be included.
#'
#' @section Usage:
#' Just drop in a chunk where you want the toc to appear (set `echo=FALSE`):
#'
#' # Table of Contents
#'
#' ```{r echo=FALSE}
#' render_toc("/path/to/the/file.Rmd")
#' ```
#'
#' @param filename Name of RMarkdown or Markdown document
#' @param toc_header_name The table of contents header name. If specified, any
#' header with this format will not be included in the TOC. Set to `NULL` to
#' include the TOC itself in the TOC (but why?).
#' @param base_level Starting level of the lowest header level. Any headers
#' prior to the first header at the base_level are dropped silently.
#' @param toc_depth Maximum depth for TOC, relative to base_level. Default is
#' `toc_depth = 3`, which results in a TOC of at most 3 levels.
render_toc <- function(
filename,
toc_header_name = "Table of Contents",
base_level = NULL,
toc_depth = 3
) {
x <- readLines(filename, warn = FALSE)
x <- paste(x, collapse = "\n")
x <- paste0("\n", x, "\n")
for (i in 5:3) {
regex_code_fence <- paste0("\n[`]{", i, "}.+?[`]{", i, "}\n")
x <- gsub(regex_code_fence, "", x)
}
x <- strsplit(x, "\n")[[1]]
x <- x[grepl("^#+", x)]
if (!is.null(toc_header_name))
x <- x[!grepl(paste0("^#+ ", toc_header_name), x)]
if (is.null(base_level))
base_level <- min(sapply(gsub("(#+).+", "\\1", x), nchar))
start_at_base_level <- FALSE
x <- sapply(x, function(h) {
level <- nchar(gsub("(#+).+", "\\1", h)) - base_level
if (level < 0) {
stop("Cannot have negative header levels. Problematic header \"", h, '" ',
"was considered level ", level, ". Please adjust `base_level`.")
}
if (level > toc_depth - 1) return("")
if (!start_at_base_level && level == 0) start_at_base_level <<- TRUE
if (!start_at_base_level) return("")
if (grepl("\\{#.+\\}(\\s+)?$", h)) {
# has special header slug
header_text <- gsub("#+ (.+)\\s+?\\{.+$", "\\1", h)
header_slug <- gsub(".+\\{\\s?#([-_.a-zA-Z]+).+", "\\1", h)
} else {
header_text <- gsub("#+\\s+?", "", h)
header_text <- gsub("\\s+?\\{.+\\}\\s*$", "", header_text) # strip { .tabset ... }
header_text <- gsub("^[^[:alpha:]]*\\s*", "", header_text) # remove up to first alpha char
header_slug <- paste(strsplit(header_text, " ")[[1]], collapse="-")
header_slug <- tolower(header_slug)
}
paste0(strrep(" ", level * 4), "- [", header_text, "](#", header_slug, ")")
})
x <- x[x != ""]
knitr::asis_output(paste(x, collapse = "\n"))
}
---
title: "blogdown toc example"
author: '@gadenbuie'
date: "2/28/2018"
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
source("render_toc.R")
```
## Table of Contents {#crazy-slug-here}
```{r toc, echo=FALSE}
render_toc("blogdown-toc-example.Rmd")
```
### WONT BE INCLUDED IN TOC
# Writing
## R Markdown
This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.
When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:
```{r cars}
# This is not a header
summary(cars)
```
## Regular Code
```r
# Regular markdown code (not run)
ggplot(mtcars, aes(x = wt, y = mpg)) +
geom_point()
```
# Plots
## Including Plots {#plots-are-here .class-foo}
You can also embed plots, for example:
```{r pressure, echo=FALSE}
plot(pressure)
```
Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.
# More
## Level 1
### Level 1.a
#### Level 1.a.i
### Level 1.b
@staceyhancock
Copy link

staceyhancock commented Aug 11, 2020

Hello @gadenbuie, thanks for the function! I'm using the function to generate a TOC for several chapters in a bookdown project, but it doesn't seem to like the particular header:

#### What does 95% mean? {-}

It gives the error message:

Error in rawToChar(out) : embedded nul in string: '#what-does-95\0ean?' Calls: <Anonymous> ... <Anonymous> -> move_files_html -> vapply -> FUN -> rawToChar In addition: Warning message: In FUN(X[[i]], ...) : out-of-range values treated as 0 in coercion to raw

Would there be a reason why the function doesn't like the % symbol?

@sai-sirpi
Copy link

sai-sirpi commented Oct 12, 2020

How can we have numbers instead of Bullet points and dashes.?

@loankimrobinson
Copy link

loankimrobinson commented Mar 18, 2021

Hi @gadenbuie, thank you very much for the nice function, it worked perfectly if I don't use cat(). I have to use cat() in my report.

For example I add this chunk codes, it didn't recognize the heading in the table of content. Can you please help me to take a look?

You can see the table of contents only test 1, test 2, and test 3, setosa, versicolor, virginica did not include in table of content

Thank you very much

library(ggplot2)
for(Species in levels(iris$Species)){
  cat('\n#', Species, '\n')
  p <- ggplot(iris[iris$Species == Species,], aes(x = Sepal.Length, y = Sepal.Width)) +
    geom_point()
  print(p)
  cat('\n')
}

Screen Shot 2021-03-18 at 1 23 41 PM

@AugustoCL
Copy link

AugustoCL commented May 29, 2021

I'm just here to support for the @Alchins question about encoding. I'm facing the same problem too. Tks.

@gadenbuie
Copy link
Author

gadenbuie commented May 30, 2021

@AugustoCL can you share an example where this function fails? I tried to create a problematic Rmd but was unable to reproduce the issue you and @Alchins describe.

@AugustoCL
Copy link

AugustoCL commented May 30, 2021

I create this .Rmd with the topics which I got problems with encoding.
https://gist.github.com/AugustoCL/52b1f861c69e577463ef6c26cddfa820
The topics are in portuguese and it's very common have accents.

@gadenbuie
Copy link
Author

gadenbuie commented May 30, 2021

@AugustoCL I just tried that example and render_toc() worked as expected. Maybe you could try adjusting the encoding argument of readLines() on line 38?

image

@AugustoCL
Copy link

AugustoCL commented May 30, 2021

I edit the encoding argument readLines() function, like you suggested and now it's working. Tks a lot for your help.

@r-leyshon
Copy link

r-leyshon commented Aug 10, 2021

Many thanks for this. Trying to get rmarkdown html output into WCAG2.1-compliant format. This function is going to help in rebuilding the TOC for html output. I made a small adjustment:

  knitr::asis_output(paste("<nav id=\"TOC\">",
                           paste(x, collapse = "\n"),
                           "</nav>", sep = "\n"))

I would like to credit you appropriately in the package docs, if you are happy for this.

@Gewerd-Strauss
Copy link

Gewerd-Strauss commented Aug 17, 2021

Is there a way to enable automatic chapter numbering comparable to the suboption 'numbered_section=true' in the normal toc-command of the yaml-header? Instead of having a bullet-point list as the TOC, maybe is it possible to recreate this with a numbered list instead?

I can't test anything right now because my system is bricked, and this is beyond my capabilities anyways. However this would be a great addition to get rid of the pesky standard TOC...

Edit 1 17.08.2021 22:00:16:
I tested it on a friend's computer, and got some weird results. Aside from the fact that numbering doesn't seem to be possible (both automatic and in-header manual numbering, surprisingly, don't show up so far), the subsections of "Methods" are not listed beneath and indented to each other as they would be in a normal toc. I don't know why this is the case. I am running Win10, tested for word, pdf and html output respectively. Not sure why this is the case.
image
image
image

Is there a way to fix this, and possibly add a method of converting to numbered sections? Especially the first one is an absolute dealbreaker right now, but judging from other people's screenshots I might be encountering a bug or I am doing some stupid mistake I am not aware of.

@statnmap
Copy link

statnmap commented Oct 9, 2021

Thank you for this gist.
It seems that blogdown is removing special characters from id in title sections, then !@:? need to be removed.
According to my test, I think this will do the trick:

h <- "éà@ù ?!: tot%" # expected: "[éà@ù ?!: tot%](éàù-tot)"

header_text <- gsub("#+\\s+?", "", h)
header_text <- gsub("\\s+?\\{.+\\}\\s*$", "", header_text) # strip { .tabset ... }
header_text <- gsub("^[^[:alpha:]]*\\s*", "", header_text) # remove up to first alpha char

# Remove special characters from slug
header_slug <- gsub("(\\W*)", "",
       strsplit(header_text, " |-")[[1]] # keep `-` if exists
  )
# Remove empty words
header_slug <- header_slug[header_slug != ""]
header_slug <- paste(header_slug, collapse = "-")
header_slug <- tolower(header_slug)

@datahua
Copy link

datahua commented May 27, 2022

Nice work! Wondering if there is anyway to change the color of the toc titles?

@manomuthus
Copy link

manomuthus commented Sep 21, 2022

Hi, this is a very useful function. Thanks. But is there a way to keep the original chapter numbers instead of bullets?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment