How to force Org to interpret Calc result as a column?

Question

Here's an example:

| low | high | students | F(students) |
|-----+------+----------+-------------|
|   0 |   30 |       15 |          15 |
|  30 |   60 |       30 |          45 |
|  60 |   70 |       40 |          85 |
|  70 |   90 |       60 |         145 |
|  90 |  100 |       15 |         160 |
#+TBLFM: @2$4..@>$4=mcol(accum(add, @2$3..@>$3), @#-1)

I hoped to do away without mcol(). For a small table like this it doesn't really matter, but, in general, this will needlessly recalculate the values as many times as there are rows. How would I avoid it?

Answer 1

This is a bad temporal solution, but it seems to be faster. There must be a better solution.

(ADDED: an important hline at the #+RESULTS output table)

#+NAME: TABLE-CUM
| students | F(students) |
|----------+-------------|
|       15 |             |
|       30 |             |
|       40 |             |
|       60 |             |
|       15 |             |
#+TBLFM: 


#+BEGIN_SRC emacs-lisp :results value :exports results :var TMP=TABLE-CUM
(require 'cl)
(setq LST (cddr TMP))                     ;; import data to list LST excluding column names and hline.
(setq VEC (apply #'mapcar* #'vector LST)) ;; transpose and change to vector VEC for function aref and aset
(setq X (first VEC))                      ;; data vector
(setq CUM (vconcat X))                    ;; temporary initial vector for cummultive sum; vconcat is required.

(dotimes (i (1- (length X)))
  (setq j (1+ i))
  (aset CUM j (+ (aref CUM (- j 1)) (aref X j))))

(setq TABLE-CUM-OUT1 (list (append X nil) (append CUM nil)))
(setq TABLE-CUM-OUT2 (apply #'mapcar* #'list TABLE-CUM-OUT1))
(append '(("students" "F(students)")) '(hline) TABLE-CUM-OUT2)
#+END_SRC

#+NAME: RESULT-TABLE-EMACS-LISP
#+RESULTS:
| students | F(students) |
|----------+-------------|
|       15 |          15 |
|       30 |          45 |
|       40 |          85 |
|       60 |         145 |
|       15 |         160 |