RStudio add-in to insert selected lines into code block:
rmd_code_block() - verbatim code block;
rmd_code_block_r() - R code block.
.
rmd_code_block_r_split() - splits block of R code.
These functions internally use function
rs_enclose_all_with_lines() -
that adds lines above and below the selection.
rmd_code_block_r() rmd_code_block() rmd_code_block_r_split()
Other R Markdown formatting add-ins: format_rmd,
rmd_equations, rmd_list