Code chunk font size in Rmarkdown with knitr and latex

Question

In knitr, the size option works fine in a .Rnw file, the following code generates:

\documentclass{article}

\begin{document}

<<chunk1, size="huge">>=
summary(mtcars)
@


\end{document}

However, I can't get it to work in Rmarkdown. The following code does not change the font size, as it did in .rnw file. The same thing happens when trying to set options with opts_chunk$set(size="huge").

Is this the expected behavior? How does one change the chunk code font size? (I mean using knitr options, not by adding \huge before the code)

---
title: "Untitled"
output: pdf_document
---

```{r, size="huge"}
summary(mtcars)
```

I am using RStudio Version 0.98.987, knitr 1.6 and rmarkdown 0.2.68.

Jempty

Unfortunately the size option only works for Rnw. For R Markdown (v2), I think the only way is to redefine the code environments for Pandoc/LaTeX (see the section "Includes" at rmarkdown.rstudio.com/pdf_document_format.html). – Lumpen

Personally I'd rather redefine environments in LaTeX instead of using hooks, because the latter approach may not be portable, e.g. you may use a chunk hook to add \begin{huge} and \end{huge} around a chunk, but then you will be stuck in LaTeX unless you do not want other document formats such as HTML, Word, ... A side comment: tweaking styles is like this kitten bothering you: i.imgur.com/17B4U.gif It is tempting to tweak the style while you work, and it is very distractive and endless work as well :) – Lumpen

Answer 1

Picking up the idea to alter a knitr hook we can do the following:

def.chunk.hook  <- knitr::knit_hooks$get("chunk")
knitr::knit_hooks$set(chunk = function(x, options) {
  x <- def.chunk.hook(x, options)
  ifelse(options$size != "normalsize", paste0("\n \\", options$size,"\n\n", x, "\n\n \\normalsize"), x)
})

This snippet modifies the default chunk hook. It simply checks if the chunk option size is not equal to its default (normalsize) and if so, prepends the value of options$size to the output of the code chunk (including the source!) and appends \\normalsize in order to switch back.

So if you would add size="tiny" to a chunk, then all the output generated by this chunk will be printed that way.

All you have to do is to include this snippet at the beginning of your document.

Butterfly

This is a great answer! – Renascent

@MartinSchmelzer: Afaik, your answer works for LaTex output only. Would you know of any handy solution which works for both HTML and LaTex? – Brower

Great answer indeed. It worked flawlessly on my local machine but failed on a server. Solution on the server was to add an extra \n as discribed by YihuI here. I have made an edit to the answer to include this. – Salivate

This is a great answer indeed if you want to a) have a LaTeX file with a lot of \small and \normalsize switches along the whole document, and b) if you want EVERY chunk to have the same size. I am using Bookdown's example environments and I don't want those to be \small. It's possible to setup this "by type of chunk" in some way? – Hieroglyphic

I think this answer, redefining the aspect of the environment is better for LaTeX, and this one, specifying it using CSS, is better for html output. – Hieroglyphic

This typically works well, but I've found that it makes it so that code chunks can't be included in incremental lists ( [#63538654 an IOSlides example of an incremental list) ) – Arrhenius

Answer 2

\tiny

```{r}
summary(mtcars)
```
\normalsize

available options for size in descending order are:
Huge > huge > LARGE > Large > large > normalsize > small > footnotesize > scriptsize > tiny

Propylene

This obliterated the use of figure references for me. – Johanson

Answer 3

Per this Gist, you have to define the font size using css:

<style type="text/css">
body, td {
   font-size: 14px;
}
code.r{
  font-size: 20px;
}
pre {
  font-size: 20px
}
</style>

code.r will control the font size for R code echoed from the code chunk, while pre will apply to any R results output from the code.

A complete working .Rmd file might look like:

---
title: "FontTest"
author: "Thomas Hopper"
date: "January 13,2016"
output: html_document
---

<style type="text/css">

body, td {
   font-size: 14px;
}
code.r{
  font-size: 20px;
}
pre {
  font-size: 20px
}
</style>

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

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

```{r cars}
summary(cars)
```

The resulting html renders as:

Deception

I believe that the original poster asks for font size change in pdf output, while your example changes the font size for html output. – Latinity

However, trying to google a solution to change font size in html output I ended here. Therefore, the answer is useful - although it wasn't for the OP. – Recent

@Tom: very useful, but when I try it I find that 'per' applies to both code and R output, with 'code.r' being unresponsive. Also, is there a way of doing this for a specific chunk? – Moncrief

Answer 4

You can define you own document format by exporting something based on the following function from your package my_package:

my_report <- function(...) {

  fmt <- rmarkdown::pdf_document(...)

  fmt$knitr$knit_hooks$size = function(before, options, envir) {
    if (before) return(paste0("\n \\", options$size, "\n\n"))
    else return("\n\n \\normalsize \n")
  }

  return(fmt)
}

This will define a knitr chunk hook size that will put the appropriate latex command before the chunk, and \normalsize after the chunk.

Anyway, with the following R markdown you can check if it's working:

---
output: my_package::my_report
---

Test text for comparison

```{r}
print(1)
```
The next code chunk has `size = 'tiny'` in the chunk options.

```{r, size = 'tiny'}
print(1)
```

I get the following result from `markdown::render():

See also the issue I opened on github:

https://github.com/yihui/knitr/issues/1296

Aromatize

Answer 5

Following up on @Martin Schmelzer's output, here's a solution in the case you want to change the code and output default font size for the whole document, but not the size of the text.

def.chunk.hook  <- knitr::knit_hooks$get("chunk")
knitr::knit_hooks$set(chunk = function(x, options) {
  x <- def.chunk.hook(x, options)
  paste0("\n \\", "size_of_the_code_and_output","\n\n", x, "\n\n \\size_of_the_text")
})

For instance,

---
output: pdf_document
---

```{r setup, include=FALSE}
def.chunk.hook  <- knitr::knit_hooks$get("chunk")
knitr::knit_hooks$set(chunk = function(x, options) {
  x <- def.chunk.hook(x, options)
  paste0("\n \\", "footnotesize","\n\n", x, "\n\n \\Huge")
})
```

# Section 1
```{r}
summary(cars)
```
Text.

# Section 2
```{r}
print(1)
```
This works for every chunks.

gives this:

Kalmia

Just what the doctor ordered! Thanks. – Gorgon