---

name: bookdown description: Cross-referencing in R Markdown documents using bookdown. Use when creating Rmd files that need references to figures, tables, equations, or sections. Triggers on requests for academic reports, technical documents, or any R Markdown with numbered cross-references.

Bookdown Cross-Referencing

Output Formats

Use bookdown:: output formats for cross-referencing support:

Copyoutput:
  bookdown::html_document2:
    toc: true
  bookdown::pdf_document2:
    toc: true

Other formats: gitbook, word_document2, epub_book.

Figures

Chunk name becomes the reference ID. Requires fig.cap:

Copy```{r myplot, fig.cap="Distribution of values."}
plot(x)

Copy
Reference: `Figure \@ref(fig:myplot)` → "Figure 1"

### Long Captions (Text Reference)

Define caption outside chunk, reference inside:

```markdown
(ref:myplot) This is a very long caption with **markdown** and citations [@smith2020].

```{r myplot, fig.cap="(ref:myplot)"}
plot(x)

Copy
## Tables

Use `knitr::kable()` with `caption`:

```r
```{r mytable}
knitr::kable(df, caption = "Summary statistics.")

Copy
Reference: `Table \@ref(tab:mytable)` → "Table 1"

## Sections

Headers auto-generate IDs from text (lowercase, hyphens):

```markdown
# My Analysis Section
See Section \@ref(my-analysis-section).

Custom ID: # My Section {#custom-id}

Equations

Copy\begin{equation}
y = mx + b
(\#eq:linear)
\end{equation}

See Equation \@ref(eq:linear).

Quick Reference

Common Issues

• References show as ??: Missing fig.cap or wrong output format
• Duplicate labels: Each chunk name must be unique
• Backslash required: Use \@ref() not @ref()