Selective export of Babel code blocks

[John Hendy <jw.hendy@gmail.com>]

I recently started a paper using Babel in a more full-functioned way
to display both R code as well as output. Previously I've just used
the convenience of headings and src blocks to create R plots and have
the code stored nicely for future reference. I'm exporting via LaTeX
to create something to promote R and why it's awesome in conjunction
with org-mode at work, which is a Minitab environment. Thus, I'd like
to include actual R code to familiarize others. On with the problem.
I'm also using tikzDevice. Thus, my paper so far is about like so:

----------
* Plotting this vs. that

Not we'll plot this vs. that. Here's the R code:

#+begin_src R :exports none
  tikzDevice("file.tex", width=6, height=4, standAlone=T)
#+end_src

#+begin_src R :exports both
  data <- read.csv("file.csv", header=T)
  sub <- subset(data, output > 5)
  ggplot(sub, aes(x=x, y=y)) + geom_point()
#+end_src

#+begin_src R :exports none
  dev.off()
  tools::texi2pdf("file.tex")
#+end_src
----------

Anyway, something like this. This isn't a huge poroblem... I'm
generating a lot of the same type of scatterplot just using different
variables, so I can copy and yank the blocks and just change
variable/file names. Doing this got me to thinking how it would be
quite neat to run code in a block but mark it to be omitted from
export for these kind of "setup" lines that are necessary for the
desired graphs but unnecessary for your reader to see over and over
again.

Thoughts? I'm quite a novice and very possibly missed something that
can already do this.


Thanks!
John