Examples of using SCons with knitr - knitr

Question

Are there minimal, or even larger, working examples of using SCons and knitr to generate reports from .Rmd files?
kniting an cleaning_session.Rmd file from the command line (bash shell) to derive an .html file, may be done via:
Rscript -e "library(knitr); knit('cleaning_session.Rmd')".
In this example, Rscript and instructions are fed to a Makefile:
RMDFILE=test
html :
Rscript -e "require(knitr); require(markdown); knit('$(RMDFILE).rmd', '$(RMDFILE).md'); markdownToHTML('$(RMDFILE).md', '$(RMDFILE).html', options=c('use_xhtml', 'base64_images')); browseURL(paste('file://', file.path(getwd(),'$(RMDFILE).html'), sep=''
In this answer https://stackoverflow.com/a/10945832/1172302, there is reportedly a solution using SCons. Yet, I did not test enough to make it work for me. Essentially, it would be awesome to have something like the example presented at https://tex.stackexchange.com/a/26573/8272.

Answer 1

[Updated] One working example is an Sconstruct file:
import os
environment = Environment(ENV=os.environ)
# define a `knitr` builder
builder = Builder(action = '/usr/local/bin/knit $SOURCE -o $TARGET',
src_suffix='Rmd')
# add builders as "Knit", "RMD"
environment.Append( BUILDERS = {'Knit' : builder} )
# define an `rmarkdown::render()` builder
builder = Builder(action = '/usr/bin/Rscript -e "rmarkdown::render(input=\'$SOURCE\', output_file=\'$TARGET\')"',
src_suffix='Rmd')
environment.Append( BUILDERS = {'RMD' : builder} )
# define source (and target files -- currently useless, since not defined above!)
# main cleaning session code
environment.RMD(source='cleaning_session.Rmd', target='cleaning_session.html')
# documentation of the Cleaning Process
environment.Knit(source='Cleaning_Process.Rmd', target='Cleaning_Process.html')
# documentation of data
environment.Knit(source='Code_Book.Rmd', target='Code_Book.html')
The first builder calls the custom script called knit. Which, in turn, takes care of the target file/extension, here being cleaning_session.html. Likely the suffix parameter is not needed altogether, in this very example.
The second builder added is Rscript -e "rmarkdown::render(\'$SOURCE\')"'.
The existence of $TARGETs (as in the example at Command wrapper) ensures SCons won't repeat work if a target file already exists.
The custom script (whose source I can't retrieve currently) is:
#!/usr/bin/env Rscript
local({
p = commandArgs(TRUE)
if (length(p) == 0L || any(c('-h', '--help') %in% p)) {
message('usage: knit input [input2 input3] [-n] [-o output output2 output3]
-h, --help to print help messages
-n, --no-convert do not convert tex to pdf, markdown to html, etc
-o output filename(s) for knit()')
q('no')
}
library(knitr)
o = match('-o', p)
if (is.na(o)) output = NA else {
output = tail(p, length(p) - o)
p = head(p, o - 1L)
}
nc = c('-n', '--no-convert')
knit_fun = if (any(nc %in% p)) {
p = setdiff(p, nc)
knit
} else {
if (length(p) == 0L) stop('no input file provided')
if (grepl('\\.(R|S)(nw|tex)$', p[1])) {
function(x, ...) knit2pdf(x, ..., clean = TRUE)
} else {
if (grepl('\\.R(md|markdown)$', p[1])) knit2html else knit
}
}
mapply(knit_fun, p, output = output, MoreArgs = list(envir = globalenv()))
})
The only thing, now, necessary is to run scons.