R in lua

R_in_lua.Rmd

---
title: "Use R in a lua filter"
output:
  html_document:
    pandoc_args: !expr rmarkdown::pandoc_lua_filter_args("my.lua")
---

This document will have uppercase header using R function `toupper()`

```{cat, engine.opts = list(file = "my.lua")}
function Header(el)
  cmd = os.getenv("R_HOME").."/bin"..os.getenv("R_ARCH").."/Rscript"
  print(cmd)
  return pandoc.walk_block(el, {
    Str = function(el)
      out = pandoc.pipe(cmd, {"dummy.R"}, el.text)
      print(out)
      return(pandoc.Str(out))
    end
  })
end
```

```{cat, engine.opts = list(file = "dummy.R")}
cat(toupper(readLines('stdin', warn = FALSE)))
```


# Something