Options should be passed like this:
<<echo=FALSE>>=
opts_chunk$set(comment="", message=FALSE,tidy.opts=list(keep.blank.line=TRUE, width.cutoff=120),options(width=100), cache=TRUE,fig.align='center',fig.height=6, fig.width=10,fig.path='figure/beamer-',fig.show='hold',size='footnotesize', cache=TRUE)
@
And here you specify width.cutoff
for code and width
for r results.