On Fri, 21 Aug 2015, Andreas Leha wrote:
Hi,
Just a small comment.
[ ... discussion of :caching of evaluation results ... ]
For purely R-based work, Charles Berry’s ox-ravel package
<https://github.com/chasberry/orgmode-accessories/blob/master/ox-ravel.org>
is a very interesting approach, since it relies on the cache feature of
knitr, which is capable of automatically detecting cross-block
dependencies like the example above under some circumstances
<http://yihui.name/knitr/demo/cache/>. It would be interesting to see
if that approach could be used to override :cache handling for ob-R,
while falling back on org-babel’s less intelligent features for other
languages (or in R environments that don’t have knitr available).
That would be just awesome!
I think I understand what Aaron is suggesting, but...
In ox-ravel exports, non-R src blocks get executed as usual, while R
blocks get converted to `chunks' for later processing by knitr or Sweave
or whatever. Anything that needs to be communicated from other languages
to R via noweb `<<run-this()>>' or `:var rvar=elisp-block()' headers
should work. That is, the resulting chunks will have code put into them
as usual in R src block execution. (And this is useful for passing latex
code to R, for example.)
But when the R code is run under knitr or some other engine outside of org
mode, it cannot communicate values back to src blocks using other
languages. Or even other R src blocks using `:var rvar=r-src-block()',
say. And it cannot use `:post' header args. I agree it would be
interesting to adapt knitr or some other dependency-aware caching engine
to run under babel control to allow R to push results to other src blocks.
I don't know how hard it would be to make it work well.
Chuck
p.s. I just pushed an org mode translation of auto-dependson.Rnw from
https://github.com/yihui/knitr-examples to the ravel-lang branch at
https://github.com/chasberry/orgmode-accessories/blob/ravel-lang/autodep.org
It illustrates automatic dependency-aware caching of R src blocks.
p.p.s. I expect to move the `ravel-lang' branch to `master' soon, so I
encourage users to try that branch.
