external_highlight(file, outfile = stdout(), theme = "kwrite",
lang = NULL, type = "HTML", line_numbers = FALSE, doc = TRUE, code)NULL, the code is simply returned as a character vectorhighlight_themes for the list
of available themes.highlight_output_types for the list
of supported output types.TRUE, the result will include line numbersTRUE, the result is a stand alone document, otherwise, just a
portion to include in a documentoutfile is given, with the side effect of writing into the file.
The result as a character vector if outfile is NULLhighlight to highlight R code using the information from the parser