knitr changing my reverse assignment operator -> to <-

问题

I am having trouble when using "reverse" assignment operators (->) in a knitr .Rnw file. For example, I have the following simple .Rnw file

\documentclass{article}
\begin{document}
<<test>>=
    options(tidy=FALSE, width=50)
    1:5 -> a
@
\end{document} 

When I use knitr to compile into a pdf, the operator -> has been reversed so the output actually has

1:5 <- a 

in it!

how can I change this?

回答1:

Make tidy=FALSE a knitr chunk option rather than an R option:

\documentclass{article}
\begin{document}
<<test,tidy=FALSE>>=
    options(tidy=FALSE, width=50)
    1:5 -> a
@
\end{document} 

(I don't think tidy=FALSE does anything at all in options(), but I guess it's harmless ...)

回答2:

For setting tidy=FALSE on a chunk-by-chunk basis, Ben's answer has got you covered.

To reset the option globally, use opts_chunk$set(), like so:

\documentclass{article}
\begin{document}

<<setup, include=FALSE, cache=FALSE>>=
opts_chunk$set(tidy=FALSE)
@

<<test>>=
1:5 -> a
@

\end{document}

---

Additionally, as documented here, tidy.opts can give you finer-grained control over many aspects of the knitr's (and ultimately formatR::tidy.source()'s) tidying behavior. Perhaps unfortunately in this case, while you can tell knitr not to replace "=" with "<-" (by doing opts_chunk$set(tidy.opts=list(replace.assign=FALSE))you cannot use that option to control whether "->" is replaced by "<-".

Here's an example that uses tidy.opts

\documentclass{article}
\begin{document}

<<setup, include=FALSE, cache=FALSE>>=
opts_chunk$set(tidy.opts=list(replace.assign=FALSE))
@

<<test>>=
j <- function(x) {  x<-y ## x<-y will be printed on new line, with added inter-token spaces
a = 1:5                  ## will be indented, but "=" won't be replaced

                       } ## closing brace will be moved to start of line
@

\end{document}

来源：https://stackoverflow.com/questions/19715551/knitr-changing-my-reverse-assignment-operator-to