At the moment, ob-R.el does not support :colnames to have a list of column
names as an argument. This seems to have been raised on the list many years
ago [1], but it does not look like it was implemented. Is there a
possibility that this could be implemented?

Also, is it possible to allow :hlines to have a list of row numbers as
arguments after which horizontal lines are drawn in the results? Could we
support a syntax such as the following

:hlines '(2 5 8)

Or something of this kind, which could then be used to draw lines after
these row numbers?

I think these two features would make it much easier to customise tables
created using R code blocks.

Would appreciate any comments and suggests.

Thanks very much and best wishes,

Vikas

[1] https://lists.gnu.org/archive/html/emacs-orgmode/2013-04/msg00499.html