075-knit-expand.Rnw

\documentclass{article}
\title{Using knit\_expand() for templates}
\author{Yihui Xie}
\begin{document}

\maketitle
\tableofcontents

\section{Write one row of data}
Only the first two sections are evaluated.
<<run-all, include=FALSE>>=
library(knitr)
src = NULL
for (i in 1:5) src = c(src, knit_expand('075-template.rnw'))
@

\Sexpr{paste(knit(text = src), collapse = '\n')}

\section{A regression model on several variables}

You can expand a template file, or just provide the template as a character string.

<<lm-mtcars, tidy.opts=list(width.cutoff=55)>>=
# the template
tpl = c("\\subsection{Regression on {{xvar}}}",
        "<<lm-{{xvar}}>>=",
        "lm(mpg~{{xvar}}, data=mtcars)",
        "@")
# expand to knitr source and pass to knit()
src = lapply(names(mtcars)[-1], function(xvar) {knit_expand(text = tpl)})
@

\Sexpr{knit(text = unlist(src))}

\section{Multiple variables}
<<multiple-tpl>>=
tpl = 'The value of a is {{a}} and b is {{b}}.'
@

\Sexpr{knit_expand(text = tpl, a = 1, b = 2)}

\Sexpr{knit_expand(text = tpl, a = 5, b = 2013)}
\end{document}