[R] Works on Mac, but not Windows: Using tempdir() to determine image location works with .tex file

[Green Stone]

I am writing an R package that generates a .pdf file for users that outputs
summarizations of data. I have a .Rnw script in the package (here, my MWE
of it is called test.Rnw). The user can do:

knit2pdf("test.Rnw", clean=T)

This makes the process easy for them, because it automatically creates the
.pdf file from the .tex file, and it erases unnecessary files for them
(.aux and .log, for example). It also stores any images into a temporary
directory (using tempdir()), which will then be erased routinely by the
system after they have been incorporated into the .tex and .pdf file. This
means they do not have to erase image files either.

Below is my test.Rnw MWE:

\documentclass[nohyper]{tufte-handout}
\usepackage{tabularx}
\usepackage{longtable}

\setcaptionfont{% changes caption font characteristics
  \normalfont\footnotesize
  \color{black}% <-- set color here}

\begin{document}
<<setup, echo=FALSE>>=
library(knitr)
library(xtable)
library(ggplot2)# Specify directory for figure output in a temporary directory
temppath <- tempdir()
opts_chunk$set(fig.path = temppath)@

  <<diamondData, echo=FALSE, fig.env = "marginfigure",
out.width="0.95\\linewidth", fig.cap = "The diamond dataset has
varibles depth and price.",fig.lp="mar:">>=
  print(qplot(depth,price,data=diamonds))@

  <<echo=FALSE,results='asis'>>=
  myDF <- data.frame(a = rnorm(1:10), b = letters[1:10])
print(xtable(myDF, caption= 'This data frame shows ten random
variables from the distribution and a corresponding letter',
label='tab:dataFrame'), floating = FALSE, tabular.environment =
"longtable", include.rownames=FALSE)@

  Figure \ref{mar:diamondData} shows the diamonds data set, with the
variables price and depth.Table \ref{tab:dataFrame} shows letters a through j
corresponding to a random variable from a normal distribution.

\end{document}

I should note that, in reality, there is another .Rnw file in my package
that calls the test.Rnw file via:

knit2pdf("/inst/Rnw/test.Rnw","/path/test.tex",clean=T)

In any case, I am trying to get this package ready to be submitted to CRAN
and have run across two problems:

1) The more perplexing question first: The MWE code above seems to work on
Mac Systems, but does not seem to work on Windows Systems! On Windows, the
.pdf file that is generated does not contain the images. After
troubleshooting, I think I have figured out the problem, but still cannot
find a solution.

Basically, on Windows, it seems that the tempdir() command will create a
pathway with double back-slashes, such as \this\is\myPath. Then, in the
.tex file, the pathway to the temporary directory (that contains the
images) are single back-slashes, such as \this\is\myPath. However, these
should be single forward-slashes, such as /this/is/myPath.

Indeed, if I manually the change the backslashes to forward slashes in the
.tex file in Windows, then I can successfully convert it to .pdf file that
successfully contains the images.

I am unsure how to solve this in my syntax, however. If I simply do
something like:

# Specify directory for figure output in a temporary directory
temppath <- tempdir()
gsub("\\\\", "/", temppath)

Then the images cannot be stored into the pathway on the Windows in the
first place, even if the .tex file will contain the correct single forward
slashes needed.

2) I am wondering if it would acceptable for me to, in my other .Rnw file,
add a second line to call:

knit2pdf("/inst/Rnw/test.Rnw","/path/test.tex",clean=T)
system(sprintf("%s", paste0("rm -r ", "/path/myFile.tex")))

So that the .tex file can also be automatically erased. I am trying to
confirm that such syntax would be acceptable by CRAN standards, as it does
involve erasing a file from the user's computer (which could seem like
dangerous/malware), although it points specifically at the .tex file it
just generated, and so it should not be deleting anything important for
them.

*Note: I am by default erasing all intermediary files so the user only
deals with the .pdf file. However, I am still allowing users the option to
go against this default, and keep these intermediary files, if needed.

I am grateful to hear any suggestions...

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