Extract R code from a template using knit_expand ()

Question

I created a dynamic document using knitr. The document makes extensive use of the package knit_expand()for templates. This is illustrated by MWE (based on the Yihui Xie example for a function).

• Main document knit-expand-MWE.Rnw

  \documentclass{article}
  
  \title{How to extract code when using\\
  knit\_expand() for templates?}%
  \author{Knitr User}
  
  \begin{document}
  
  \maketitle
  \tableofcontents
  
  \newpage
  \section{Write one row of data}
  
  Only the first two sections are evaluated.
  
  <<run-all, include=FALSE>>=
  library(knitr)
  src = NULL
  for (i in 1:3) src = c(src, knit_expand('template.Rnw'))
  @
  
  \Sexpr{paste(knit(text = src), collapse = '\n')}
  
  \end{document}
  

• The template template.Rnwcalled by the main document

  \subsection{Now i is {{i}}}
  
  This chunk is {{if (i > 2) 'not '}}evaluated.
  <<row-{{i}}, eval={{i <= 2}}>>=
  # row number {{i}}
  iris[{{i}}, ]
  @
  

Now I need to extract the corresponding R code. Execution of purl("knit-expand-MWE.Rnw")outputs knit-expand-MWE.R, which includes code in a piece with a link to a template:

## ----run-all, include=FALSE----------------------------------------------
library(knitr)
src = NULL
for (i in 1:3) src = c(src, knit_expand('template.Rnw'))

Instead, I need the appropriate “advanced” code (for colleagues who don’t use knitr), for example:

## ----row-1, eval=TRUE----------------------------------------------
## row number 1
iris[1, ]

## ----row-2, eval=TRUE----------------------------------------------
## row number 2
iris[2, ]

## ----row-3, eval=FALSE----------------------------------------------
## row number 3
iris[3, ]

How can i achieve this?

Answer 1

purl() src, e. .

purl(text = src, output = 'knit-expand.R')