How to create R-markdown sections inside a R code chunk? With proper code display

Question

I am currently writing on a report with rmarkdown and therefore I want to create sections inside a r code chunk. I figured out that this is possible with the help of

Answer 1

Using markdown and the verbatim environment

You could surround R output with verbatim environment, escape code with four \in chunks.

```{r, results='asis'}
for (i in 1:10) {
  cat("\\section{Part:", i, "}")
  cat("\\begin{verbatim}")
  print(summary(lm(data=mtcars, mtcars[,1]~ mtcars[,i])))
  cat("\\end{verbatim}")
  cat(paste0("$\\\\alpha$ = ", mtcars[1,i]))  
}
```

Something more fancy using the listings package

At some point, when running latex, I tend to quit markdown (.Rmd) and use sweave (.Rnw), I find it much more easy, you can check what's happening in .tex files and figure out what's wrong.

\documentclass[a4paper]{article}
\usepackage{listings}
\usepackage[usename,dvipsnames]{xcolor}
% create a set of colors
\definecolor{mygreen}{rgb}{0,0.6,0} 
\definecolor{mygray}{rgb}{0.5,0.5,0.5}
\definecolor{mymauve}{rgb}{0.58,0,0.82}
% create a listings environment suitable for R code
\lstset{ %
  backgroundcolor=\color{white},   % choose the background color; you must add \usepackage{color} or \usepackage{xcolor}
  basicstyle=\footnotesize\ttfamily, % the size of the fonts that are used for the
  % code
  breakatwhitespace=false,         % sets if automatic breaks should only happen at whitespace
  breaklines=true,                 % sets automatic line breaking
  captionpos=b,                    % sets the caption-position to bottom
  commentstyle=\color{mygreen},      % comment style
  deletekeywords={...},            % if you want to delete keywords from the given language
  escapeinside={\%*}{*)},          % if you want to add LaTeX within your code
  extendedchars=true,              % lets you use non-ASCII characters; for 8-bits encodings only, does not work with UTF-8
  frame=single,                    % adds a frame around the code
  keepspaces=true,                 % keeps spaces in text, useful for keeping indentation of code (possibly needs columns=flexible)
  keywordstyle=\color{blue},       % keyword style
  language=R,                       % the language of the code
  morekeywords={*,...},            % if you want to add more keywords to the set
  numbers=left,                    % where to put the line-numbers; possible values are (none, left, right)
  numbersep=5pt,                   % how far the line-numbers are from the code
  numberstyle=\tiny\color{mygray},   % the style that is used for the line-numbers
  rulecolor=\color{black},         % if not set, the frame-color may be changed on line-breaks within not-black text (e.g. comments (green here))
  showspaces=false,                % show spaces everywhere adding particular underscores; it overrides 'showstringspaces'
  showstringspaces=false,          % underline spaces within strings only
  showtabs=false,                  % show tabs within strings adding particular underscores
  stepnumber=2,                    % the step between two line-numbers. If it is 1, each line will be numbered
  stringstyle=\color{mymauve},      % string literal style
  tabsize=2,                       % sets default tabsize to 2 spaces
  title=\lstname                   % show the filename of files included with \lstinputlisting; also try caption instead of title
}
\title{test}
\begin{document}
\maketitle

<<r, results='asis'>>=
for (i in 1:10) {
  cat("\\section{Part:", i, "}")
  cat("\\begin{lstlisting}")
  print(summary(lm(data=mtcars, mtcars[,1]~ mtcars[,i])))
  cat("\\end{lstlisting}")
  cat(paste0("$\\\\alpha$ = ", mtcars[1,i]))  
}
@

\end{document}