How to make a figure caption in Rmarkdown? - knitr

Question

I am thinking about writing my thesis with rmarkdown and latex. I'm getting the hang of how it all works, however, when I try to add a figure (not an R plot) to the text and render it to pdf, the caption and in-text reference dissappear.
This is the code snippet I use to add a figure:
---
title: "Untitled"
output: pdf_document
---
see figure \ref{fig1}.
![picture \label{fig1}](figure1.png)
This is what knitr creates:
This is what pandoc creates:
Question:
How do I make figure captions and in-text references to those figures in Rmarkdown that will display when rendered to pdf?
OR
How do I tell pandoc what Rmarkdown is so it will render R code and plots?

Answer 1

Please see the documentation of R Markdown for PDF output, and in particular, look for fig_caption. Figure captions are turned off by default in R Markdown, and you have to turn them on (fig_caption: true). You can also find this setting from the gear button on the toolbar of RStudio IDE.

Answer 2

Update: please check https://github.com/yihui/knitr/issues/1063.
Question: How do I make figure captions and in-text references to those figures in Rmarkdown that will display when rendered to pdf?
To get the cross-reference in the PDF produce by LaTeX you need to run LaTeX more than once. Some LaTeX IDE does it for you.
knitr is only running LaTeX once and that is the reason that you only get ??. To confirm that this was the problem I ran
library(knitr)
knitr()
in R that returned
see figure \ref{fig1}.
\begin{figure}[htbp]
\centering
\includegraphics{imagem.jpg}
\caption{picture \label{fig1}}
\end{figure}
which is a valid LaTeX code.
How do I tell pandoc what Rmarkdown is so it will render R code and plots?
Pandoc only understand Markdown (not RMarkdown). First you have to call knitr to generate the Markdown from the RMarkdown and after it call Pandoc to convert the Markdown to LaTeX.

Answer 3

I just found a very useful solution here.
First, include the following chunk:
```{r functions, include=FALSE}
# A function for captioning and referencing images
fig <- local({
i <- 0
ref <- list()
list(
cap=function(refName, text) {
i <<- i + 1
ref[[refName]] <<- i
paste("Figure ", i, ": ", text, sep="")
},
ref=function(refName) {
ref[[refName]]
})
})
```
After, we can add the caption of the figure/table in the figure chunk options like:
```{r, fig.cap=paste("Your caption.")}
See that fig.cap works better with paste.

Answer 4

In Rmarkdown
for markdown figures
![caption \label{labelx}](link_to_figure, or path of figure){figure dimensions}
# how to cite markdown figure
\ref{labelx}
for latex figures
Add following in the figure environment of latex which starts with
\begin{figure}
includegraphics[]{/path to figure}
\label{label}
\end{figure}
# how to cite latex
\ref{label}
for bookdown
add chunk names as label names like
{r label2,echo=F}
# to cite by using bookdown use
\#ref(fig:label2)
similarly for tab we cite table as \#ref(tab:table_label)
For captioner package
add a chunk at the top of rmarkdown document
tab_cap <- captioner(prefix = "table")
fig_cap <- captioner(prefix = "figure")
where prefix is the prefix for cross referencing a figure.
add this in chunk options
{r fig_cap("labelforcaptioner","caption for captioner figure"}
note that fig_cap is similar to fig_cap in chunk code for captioner.
and to cite use
`r fig_cap("label4",display='cite')