render_post.R

#!/usr/bin/env Rscript
options(stringsAsFactors = FALSE)

# inspiration sources:
# http://www.jonzelner.net/jekyll/knitr/r/2014/07/02/autogen-knitr/
# http://gtog.github.io/workflow/2013/06/12/rmarkdown-to-rbloggers/

KnitPost <- function(bashwd = "", convert_file = "", overwrite = FALSE, date="") {
   # CONVERT ALL RMD FILES TO MARKDOWN?
   #    REQUIRED: overwrite
   # CONVERT A SPECIFIC RMD FILE TO MARKDOWN?
   #    REQUIRED: bashwd, convert_file

   # bashwd: working directory (passed on from bash, only used below
   #         if a specific Rmd file is to be converted)
   # convert_file: name/path to specific Rmd file to convert
   # overwrite: flag that tells us whether to overwrite md files
   #            when converting all Rmd files

   # directory of jekyll blog (including trailing slash)
   site.path <- "~/Code/terencekwt.github.io/"
   # directory where your Rmd-files reside (relative to base)
   rmd.path <- paste0(site.path, "_knitr")
   # directory to save figures
   fig.dir <- "figures/"
   # directory for converted markdown files
   posts.path <- paste0(site.path, "_posts")
   # cache
   cache.path <- paste0(site.path, "_cache")

   require(knitr)
   render_jekyll(highlight = "pygments")
   # "base.dir is never used when composing the URL of the figures; it is
   # only used to save the figures to a different directory, which can
   # be useful when you do not want the figures to be saved under the
   # current working directory.
   # The URL of an image is always base.url + fig.path"
   # https://groups.google.com/forum/#!topic/knitr/18aXpOmsumQ
   opts_knit$set(
      base.url = "/",
      base.dir = site.path)
   opts_chunk$set(
      fig.path   = fig.dir,
      fig.width  = 8.5,
      fig.height = 5.25,
      dev        = 'svg',
      cache      = FALSE,
      warning    = FALSE,
      message    = FALSE,
      cache.path = cache.path,
      tidy       = FALSE)


   if (convert_file == "") {
      # convert all Rmd files in {site-url}/_knitr/ to markdown files
      # contingent on whether overwrite requested and if md exists

      # setwd to Rmd folder
      setwd(rmd.path)

      files.rmd <-
         data.frame(rmd = list.files(
            path = rmd.path,
            full.names = TRUE,
            pattern = "\\.Rmd$",
            ignore.case = TRUE,
            recursive = FALSE))

      files.rmd$corresponding.md.file <-
         paste0(posts.path, "/",
            basename(gsub(pattern = "\\.Rmd$",
               replacement = ".md",
               x = files.rmd$rmd)))

      files.rmd$corresponding.md.exists <-
         file.exists(files.rmd$corresponding.md.file)
      files.rmd$md.overwrite <- overwrite
      files.rmd$md.render <- FALSE
      # check if corresponding md file exists for each Rmd file,
      # if not, set flag to convert to markdown
      # (also consider the overwrite flag set by user)
      for (i in 1:dim(files.rmd)[1]) {
         if (files.rmd$corresponding.md.exists[i] == FALSE) {
            files.rmd$md.render[i] <- TRUE
         }
         if ((files.rmd$corresponding.md.exists[i] == TRUE) &&
             (files.rmd$md.overwrite[i] == TRUE)) {
            files.rmd$md.render[i] <- TRUE
         }
      }

      # For each Rmd file, render markdown (contingent on the flags set above)
      for (i in 1:dim(files.rmd)[1]) {
         # only re-knit if overwrite==TRUE or .md not already existing
         if (files.rmd$md.render[i] == TRUE) {
            # KNITTING ====
            message(paste0("=== KnitPost(overwrite=", overwrite, "): ",
                           basename(files.rmd$rmd[i])))
            out.file <-
               knit(files.rmd$rmd[i],
                  output = files.rmd$corresponding.md.file[i],
                  envir = parent.frame(),
                  quiet = TRUE)
         }
      }
   } else {
      # convert a single Rmd file to markdown
      # setwd to bash pwd
      setwd(bashwd)
      convert.path <- paste0(bashwd, "/", convert_file)
      md.path <-
         paste0(posts.path, "/", date, "-",
         basename(gsub(pattern = "\\.Rmd$",
            replacement = ".markdown",
            x = convert_file)))
      # KNITTING ====
      message(paste0("=== KnitPost(", convert.path, ")"))
      out.file <-
         knit(convert.path,
            output = md.path,
            envir = parent.frame(),
            quiet = TRUE)
   }
}