How does knitr inject TeX code into the document?

Question

I'm very new to knitr. How do I write R code in knitr that composes LaTeX from scratch and injects it into the document at a particular point?

I'm thinking of something similar to what PHP or JSP does.

Answer 1

TeX is a text for knitr, so you can use any text-generating function, e.g. cat(). To include the text into the document, add echo=FALSE, results='asis' to the chunk options, e.g.

<<echo=FALSE,results="asis">>=
title="Introduction"
cat(paste("\\section{",title,"}",sep=""))
@ 

which adds to your document \section{Introduction}