I want to have the ability to execute statements on R's REPL with the option to pipe it to a buffer so I can quickly refer back to it later.
To run a shell command and output to *shell command buffer* I can use M-! as per this question. What would the equivalent be for R's REPL without resorting to write.csv()?
You can use ess-command from ess-inf to redirect the output to another buffer. An example could look like the following,
(defun redirect-ess-output (command &optional buffer process)
(interactive (list (read-from-minibuffer "Command: ")))
(let ((buff (get-buffer-create (or buffer "*r-output*")))
;; 'ess-get-process' defaults to process local to current
;; buffer, so to call from anywhere default to "R"
(proc (ess-get-process (or process "R"))))
;; send a trailing newline to process
(unless (string-match-p "\n$" command)
(setq command (concat command "\n")))
(ess-command command buff 'sleep nil nil proc)
(with-current-buffer buff
;; process stuff
(pop-to-buffer buff))))
