an output file name passed to writeLines,
or NULL (no file written).
header
logical, if a yaml header (enclosed between triple dashes, ---)
is to be parsed.
extra
character, optional string that is placed into the code chunk openings.
Author
Peter Solymos <solymos@ualberta.ca>
Details
Leading double hashes ## treated as non-code.
Leading # followed by other than # is code comment.
Leading # after whitespace is code comment.
A newline is code when preceded and followed by code.
The leading double hash ## is trimmed for comment lines.
R markdown chunk start/end stuff is added for code chunks.
The argument extra adds chunk arguments, e.g.
extra=', eval=FALSE' etc. See R markdown website at
https://rmarkdown.rstudio.com/