Figure label printed in the caption using `bookdown::pdf_book()`

[phargarten2]

When using bookdown::pdf_book(), the figure label is automatically printed inside the caption.

Here is an example R-markdown document.

---
title: "Example"
author: "Paul Hargarten"
date: "5/22/2020"
output:
 bookdown::pdf_book
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

You can also embed plots (Figure \ref{fig::plots}), for example:

```{r pressure, echo = FALSE, fig.cap = "\\label{fig::plots} Some caption."}
plot(pressure)
```

But if I use `knitr::include_graphics()`, the label shows up in the caption of the picture. 

```{r fig.r, fig.pos="h", echo=FALSE, fig.cap="\\label{fig::R} R is a flexible statistical program."}
knitr::include_graphics("Rlogo.pdf")
```

R is great (Figure \ref{fig::R}).


There is no label shown when I use `rmarkdown::pdf_document()`. 
```

Using this image Rlogo.pdf, compiling this document yields
Example_for_StackOverflow.pdf.

The following contains the figure legend in the pdf file.

Figure 2: (#fig:fig.r) R is a flexible statistical program.

Is it possible to remove the figure label from the compiled caption? Thanks!

---

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NOTE: Due to the inability of saving files for a reproducible example on Stack Overflow, I am posting my issue here.

[yihui]

Where is your Stack Overflow post? (The issue guide asked you to provide the link to the post) Thanks!

[phargarten2]

I did not make one. As I am unable to save files for a reproducible example on Stack Overflow, I posted the issue here.

[jogrue]

I stumbled upon the same issue and just in case of someone landing here as well: Apparently, R chunk names containing spaces, dots, or underscores (and maybe other special characters) are not correctly translated to labels in Latex. In the example below, instead of \caption{\label{tab:my.table}This is my table.} it becomes \caption{(\#tab:my.table)This is my table).} I do not know if this is the intended behavior or if it is a Latex limitation.

What worked for me, was restricting the chunk labels to simple one-word labels or only using regular hyphens.

Just a test. See Table \@ref(tab:my.table).

```{r my.table}
knitr::kable(
  data.frame(
    cbind(
      numbers = c(1, 2, 3),
      letters = c("a", "b", "c")
    )
  ),
  caption = "This is my table."
)
```

[MilesMcBain]

Thankyou so much @jogrue!

I was getting this HTML output:

Removing the _'s in the chunk names has caused the figure labels to render correctly. :+1:

Perhaps using underscores or other special chars in chunk names with a figure caption should cause a warning?

[cderv]

About the special characters in labels, this is related to other issues raised in the past with that: https://github.com/rstudio/bookdown/issues/839 https://github.com/rstudio/bookdown/issues/157 https://github.com/rstudio/bookdown/issues/941 https://github.com/rstudio/bookdown/issues/867 https://github.com/rstudio/bookdown/issues/406 https://github.com/rstudio/bookdown/issues/194 https://github.com/rstudio/bookdown/issues/336

This is indeed documented (in https://bookdown.org/yihui/bookdown/figures.html)

If you want to cross-reference figures or tables generated from a code chunk, please make sure the chunk label only contains alphanumeric characters (a-z, A-Z, 0-9), slashes (/), or dashes (-).

but the idea of a warning has also been already proposed. This impact only bookdown when labels is used for referencing but maybe we can detect when it is used and do something about this.