## 3.4 A single document

Sometimes you may not want to write a book, but a single long-form article or report instead. Usually what you do is call rmarkdown::render() with a certain output format. The main features missing there are the automatic numbering of figures/tables/equations, and cross-referencing figures/tables/equations/sections. We have factored out these features from bookdown, so that you can use them without having to prepare a book of multiple Rmd files.

The functions html_document2(), tufte_html2(), pdf_document2(), word_document2(), tufte_handout2(), and tufte_book2() are designed for this purpose. If you render an R Markdown document with the output format, say, bookdown::html_document2, you will get figure/table numbers and be able to cross-reference them in the single HTML page using the syntax described in Chapter 2.

The above HTML and PDF output format functions are basically wrappers of output formats bookdown::html_book and bookdown::pdf_book, in the sense that they changed the base_format argument. For example, you can take a look at the source code of pdf_document2:

bookdown::pdf_document2
## function(...) {
##   pdf_book(..., base_format = rmarkdown::pdf_document)
## }
## <environment: namespace:bookdown>

After you know this fact, you can apply the same idea to other output formats by using the appropriate base_format. For example, you can port the bookdown features to the jss_article format in the rticles package (Allaire, R Foundation, et al. 2018) by using the YAML metadata:

output:
bookdown::pdf_book:
base_format: rticles::jss_article

Then you will be able to use all features we introduced in Chapter 2.

Although the gitbook() format was designed primarily for books, you can actually also apply it to a single R Markdown document. The only difference is that there will be no search button on the single page output, because you can simply use the searching tool of your web browser to find text (e.g., press Ctrl + F or Command + F). You may also want to set the option split_by to none to only generate a single output page, in which case there will not be any navigation buttons, since there are no other pages to navigate to. You can still generate multiple-page HTML files if you like. Another option you may want to use is self_contained = TRUE when it is only a single output page.

### References

Allaire, JJ, R Foundation, Hadley Wickham, Journal of Statistical Software, Yihui Xie, Ramnath Vaidyanathan, Association for Computing Machinery, et al. 2018. Rticles: Article Formats for R Markdown.