Question: I've just started using Sweave on TeXShop ( which runs on OSX). Is it possible to have syntax coloring of the source code so that I can distinguish between raw text and R-code? 

For example, the following code snippet in my Sweave file is the same as the rest of the text, which makes it harder to read than an R editor that has syntax coloring.

```
<<reg, fig=TRUE, echo=FALSE>>=
a = c(10,15)
plot(a, a)
@

```

(I have also tried this out using the wonderful [RStudio](http://www.rstudio.org/) which does have syntax coloring for both R and Latex, but I think TexShop is superior for LaTeX.)

Answer: 
I don't believe TexShop supports mode switching (e.g. highlighting in two different languages--R and LaTeX--within the same file), since it was designed around a single language (LaTeX). Editors that do and therefore properly handle Sweave are to my knowledge:

* Eclipse with Stat/ET
* RStudio
* Emacs with ESS
Actually, you can use highlighted syntax out of the box. Use `pgfSweave` package. Just add `pgf=TRUE` (and `echo=TRUE`) to your Sweave chunk, and you're good to go. Install `pgfSweave`, and load a package vignette (`vignette("pgfSweave")`) for further assistance.

> 
> Version 1.1.0 of pgfSweave introduced
>  the highlight option. The default is
>  TRUE by default so code will be
>  syntax-highlighted with the highlight
>  package.
> 
> 
>