I am relatively new to Sweave, and R in general and have been having issues trying to render basic math symbols in my plot labels. I believe the problem may be cause by either Sweave or tikzDevice package as I am able to render the math symbols perfectly fine if I use either a png or pdf device.
Writing this code to either a png or pdf device gives expected output --the > symbol
qplot(factor(cyl), data=mtcars, geom="bar", colour=factor(cyl)) + scale_x_discrete(paste("",">","6k"))
Using .tex output file resulting from running Sweave on file below replaces > symbol with ¿ symbol
<<fig=FALSE, echo=FALSE>>=
require(tikzDevice)
require(ggplot2)
require(reshape2)
tikz('sweave-math-symbols.tex', width=5.9, height=2.7)
qplot(factor(cyl), data=mtcars, geom="bar", colour=factor(cyl)) + scale_x_discrete(paste("",">","6k"))
@
LaTeX document that uses output file from Sweave is below
\documentclass[a4paper,10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
%opening
\title{Sweave Math Symbols}
\author{Phiri}
\begin{document}
\maketitle
\begin{abstract}
\end{abstract}
\section{Illustration}
\input{sweave-math-symbols.tex}
\end{document}
Where is this problem stemming from and how do I go about fixing it?
Your Sweave file worked for me without modification (on Ubuntu 10.04), but you might try wrapping the > in TeX math delimiters ($$, i.e. $>$); frankly, I'm surprised that /don't understand why it works OK without the delimiters in some contexts.