knitr: Add figure notes

Question

I have a figure that looks like this:

<<foo, fig.lp='', fig.cap='name', fig.subcap=c('left', 'right'),>>=
plot1
plot2
@

Now I would like to display a set of notes about this figure right below (i.e. a multiline text). Is there any convenient way to do this within the figure environment created by knitr?

---

As already pointed out in the comments above, there is currently no solution to my problem. I have filed a feature request.

Answer 1

I know this is a really late answer but here is what I ended up doing for the same type of a problem.

I defined a custom hook that would plot the image as I want it

# Custom knitr hook to add notes to the plot
knit_hooks$set(plot = function(x, options) {
  paste("\n\\end{kframe}\n\\begin{figure}\n",
        "\\includegraphics[width=\\maxwidth]{",
        opts_knit$get("base.url"), paste(x, collapse = "."),
        "}\n",
        "\\textsc{Note} -- here is some car stuff with notes",
        "\\caption{", options$fig.cap, "}\n",
        "\n\\end{figure}\n\\begin{kframe}\n",
        sep = '')
})

Here is the full .Rnw

\documentclass{article}

\usepackage[font=large,labelfont=sc]{caption}

\begin{document}

<<setup, echo=FALSE, message=FALSE, results='hide'>>=
suppressPackageStartupMessages({
  library(ggplot2)
})

opts_chunk$set(echo=FALSE)
opts_chunk$set(results="hide")
@

<<foo, fig.cap='with notes', fig.height=4, fig.width=6>>=
# save a regular plotting function
regular_plot <- knit_hooks$get("plot")

# Custom knitr hook to add notes to the plot
knit_hooks$set(plot = function(x, options) {
  paste("\n\\end{kframe}\n\\begin{figure}\n",
        "\\includegraphics[width=\\maxwidth]{",
        opts_knit$get("base.url"), paste(x, collapse = "."),
        "}\n",
        "\\textsc{Note} -- here is some car stuff with notes",
        "\\caption{", options$fig.cap, "}\n",
        "\n\\end{figure}\n\\begin{kframe}\n",
        sep = '')
})

ggplot(data = mtcars) + geom_point(aes(disp,mpg))
@

<<bar, fig.cap='without notes', fig.height=4, fig.width=6>>=
# restore regular plotting function
knit_hooks$set(plot = regular_plot)

ggplot(data = mtcars) + geom_point(aes(disp,mpg))
@

\end{document}

and here is the resulting PDF:

Answer 2

akhmed answer was absolutely amazing!

I made an slighly modification for Rmd to get caption first and to generalize for every chunk in the document.

We have to add these lines at the beginning:

knit_hooks$set(plot = function(x, options, .notes = notes, .sources = sources) {
  paste("\n\n\\begin{figure}\n",
        "\\includegraphics[width=\\maxwidth]{",
        opts_knit$get("base.url"), paste(x, collapse = "."),
        "}\n",
        "\\caption{",options$fig.cap,"}","\\label{fig:",opts_current$get("label"),"}","\\textsc{}",
        "\n\\textsc{Notas} -- ",.notes,
        "\n\\textsc{Fuentes} -- ", .sources,
        "\n\\end{figure}\n",
        sep = '')
})

Then in every chunk we only write the notes and sources of the plot

notes = "Notes to explain the plot"
sources = "Explain the sources"

Again, thanks a lot akhmed!!

Pd: I use "\\textsc{}" to generate an space among caption and notes & sources.

It would be nice to generalize this to use subcaptions with many figures in the same plot.

Answer 3

The solution from @akhmed was enormously helpful for me. I needed to make a few additional customizations which I pass along as an answer (it was too long for a comment).

• First, I wanted a little more control over the margins for the note and found adding the minipage environment helped (\\begin{minipage} below set at 6 inches wide).

• Second, I added a couple of minor formatting additions by setting a typeface size and left justifying the text (\\small and \\begin{flushleft} below).

• Finally, for some figures, I wanted to use the fig.pos="h!" or figure position = "here" option of Knitr / Latex and it took me a minute to realize that this hook overwrites that chunk option so I manually added it as \\begin{figure}[h!].

Again, my thanks to @akhmed for offering this solution.

knit_hooks$set(plot = function(x, options) {
    paste("\n\\end{kframe}\n\\begin{figure}[h!]\n",
      "\\includegraphics[width=\\maxwidth]{",
      opts_knit$get("base.url"), paste(x, collapse = "."),
      "}\n",
      "\\begin{minipage}{6in}\\small\\begin{flushleft}Note: Lorem ipsum \\end{flushleft}\\end{minipage}",
      "\\caption{", options$fig.cap, " \\label{", options$fig.lp, opts_current$get("label"), "}}\n",
      "\n\\end{figure}\n\\begin{kframe}\n",
      sep = '')
    })