Reduce space between code chunks and code output in rmarkdown beamer presentation - latex

Question

I'm building a presentation using rmarkdown and LaTeX/Beamer. I would like to reduce the spacing between the displayed R-commands and R-output. I believe this is related to the paragraph spacing options in LaTeX/Beamer.
Is this something I should do in rmarkdown (chunk options, knit_hooks, or something else?), in the pandoc Yaml header (some pandoc option?), or in the LaTeX beamer template file? I feel like it should be in the LaTeX template file.
Below is a working example of a minimal markdown file, and a .tex template file I'm using to control some beamer settings.
example.Rmd
---
title: "Untitled"
author: "Ryan"
date: "March 1, 2016"
output:
beamer_presentation:
pandoc_args: '--latex-engine=xelatex'
includes:
in_header: latex-topmatter.tex
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## Vertical Spacing is too much
Here is a working example.
- some
- bullets
Example code:
```{r, echo = TRUE}
a <- 1
a
a+a
```
latex-topmatter.tex
% declare overall beamer theme to use as baseline
\usetheme{default}
% make code-output smaller
\DefineVerbatimEnvironment{Highlighting}{Verbatim}{fontsize=\tiny,commandchars=\\\{\}}
% make console-output smaller:
\makeatletter
\def\verbatim{\tiny\#verbatim \frenchspacing\#vobeyspaces \#xverbatim}
\makeatother
% set vertical spacing between paragraphs:
% \parskip{0pt}
% \addtobeamertemplate{blocks}{}{\setlength{\parskip}{0pt}}
% \addtobeamertemplate{block begin}{}{\setlength{\parskip}{0pt}}
% \addtobeamertemplate{block end}{}{\setlength{\parskip}{0pt}}
% % \setlength{\emergencystretch}{0em}
\setlength{\parskip}{0pt}
I've tried making the font of the R-commands or R-output smaller, which does not seem to affect the paragraph spacing.
I've tried using knit_hooks() as in this example:
https://github.com/ramnathv/slidify/issues/189, which mostly works - but then i can't seem to reduce the fontsize of the code and output.
I've also tried using \parskip{0pt}, and several other beamer options or parskip options, which are commented in the above latex-topmatter.tex section. None of them seem to change the spacing between chunks of text, R-code, or R-output. Am I even looking in the right place?

Answer 1

Here is a working example. Notice the definitions at the end of the header file:
Source code chunks are contained inside a Shaded environment which in turn uses \OuterFrameSep for its spacing. So we need to redefine that.
With \preto we prepend the commands \topsep=-10pt \partopsep=-10pt to every verbatim environment. This affects the spacing of output chunks.
example.Rmd
---
title: "Untitled"
author: "Martin"
date: "January 4, 2017"
output:
beamer_presentation:
keep_tex: yes
pandoc_args: --latex-engine=xelatex
includes:
in_header: latex-topmatter.tex
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## Vertical Spacing is just right
Here is a working example.
- some
- bullets
Example code:
```{r, echo = TRUE}
a <- 1
a
a+a
```
latex_topmatter.tex
% declare overall beamer theme to use as baseline
\usetheme{default}
% make code-output smaller
\DefineVerbatimEnvironment{Highlighting}{Verbatim}{fontsize=\tiny,commandchars=\\\{\}}
% make console-output smaller:
\makeatletter
\def\verbatim{\tiny\#verbatim \frenchspacing\#vobeyspaces \#xverbatim}
\makeatother
\setlength{\parskip}{0pt}
\setlength{\OuterFrameSep}{-4pt}
\makeatletter
\preto{\#verbatim}{\topsep=-10pt \partopsep=-10pt }
\makeatother