How can one make RStudio pass options to Sweave()?

Question

I'm trying to use a UTF-8 encoded .Rnw file in combination with xelatex in RStudio. Since xelatex uses native UTF-8 support i cannot use

\usepackage[utf8]{inputenc}

in my .Rnw file, which would ensure that the encoding auto-guessing of Sweave() works properly. The only other option I know of is to run

Sweave(..., encoding="utf8")

however, I don't know how to configure RStudio to call Sweave() that way. Is there an option in RStudio for that, or any other way to pre-set this option for Sweave?

Answer 1

Although Sweave guesses the file encoding from \usepackage[foo]{inputenc}, RStudio does not guess, because it is an editor, and it knows the encoding precisely. In fact, RStudio just passes the encoding to utils::Sweave() directly, so you are totally fine without \usepackage[utf8]{inputenc} when using XeLaTeX. You need to make sure you are using the latest version of RStudio, since I do not remember which version of RStudio this feature was added to (but I'm pretty sure the latest version has it). The same thing is applied to knitr, which does not guess the encoding at all.