Elisp in org-mode for counting tag groups (lemmy.ml)

submitted 8 months ago by edumerco@lemmy.ml to c/emacs@lemmy.ml

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Dear emacs and org-mode comrades.

Given:

a table with
- a list of tags +
- their number of appearances in question 1 (Q1) & and question 2 (Q2).
org support for tag groups (https://orgmode.org/manual/Tag-Hierarchy.html)
3 defined tag groups
- GroupTag1 (GT1)=tagA+tagC+tagD and
- GroupTag2 (GT2)=tagB+tagE
- GroupTag3 (GT3)=tagB+tagC+tagD (yes, some tags are in more than 1 group)

How can I count with pure elisp (assuming some table formula but I'm open to other ways) the sum of individual tag appearances of each tag group, for each question?

Example:

| tag  | Q1 | Q2 |
|------+----+----|
| tagA |  9 |    |
| tagB |  4 |  2 |
| tagC |  1 |  4 |
| tagD |    |  5 |
| tagE |    |  6 |
|------+----+----|
| GT1  | 10 |  9 |
| GT2  |  4 |  9 |
| GT3  |  5 | 11 |

Thanks a lot for your time and attention... :)

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[-] sachac@lemmy.ml 3 points 8 months ago* (last edited 4 months ago)

Edit 2026-01-07: added the missing ) and fixed the formatting

Here's how I would approach it:

#+STARTUP: noptag
#+TAGS:
#+TAGS: [ GT1 : tagA tagC tagD ]
#+TAGS: [ GT2 : tagB tagE ]
#+TAGS: [ GT3 : tagB tagC tagD ]

#+NAME: source
| tag  | Q1 | Q2 |
|------+----+----|
| tagA |  9 |    |
| tagB |  4 |  2 |
| tagC |  1 |  4 |
| tagD |    |  5 |
| tagE |    |  6 |

#+begin_src emacs-lisp
(defun my-sum-tag-groups (source)
  (cons
   (car source)
   (mapcar
    (lambda (tag-group)
      (let ((tags (org--tags-expand-group (list (car tag-group)) org-tag-groups-alist nil)))
        (cons
         (car tag-group)
         (seq-map-indexed
          (lambda (colname i)
            (apply
             '+
             (mapcar
              (lambda (tag)
                (let ((val (or (elt (assoc-default tag source) i) "0")))
                  (if (stringp val)
                      (string-to-number val)
                    (or val 0))))
              tags)))
          (cdr (car source))))))
    org-tag-groups-alist)))
#+end_src

#+begin_src emacs-lisp :var source=source :colnames no :results table
(my-sum-tag-groups source)
#+end_src

#+RESULTS:
:results:
| tag | Q1 | Q2 |
| GT1 | 10 |  9 |
| GT2 |  4 |  8 |
| GT3 |  5 | 11 |
:end:

[-] edumerco@lemmy.ml 2 points 7 months ago

Dear @sachac@lemmy.ml

I checked here day after day but didn't saw your reply under mine until now, I'm so sorry...

Thank you very much, I will check it right now and come back soon. Slowly, but surely, this is going forward.

Again, thank you very much. nn(^‿^)nn b(^‿^)d

[-] edumerco@lemmy.ml 1 points 7 months ago

Dear @sachac (BTW, are you the legendary Sacha Chua?)

There was a parenthesis missing in the end, but it is working!!! :)))

I still have to understand the scope (does it works on the heading/ tree where it is called only, can I "point it" to a specific table, etc.) but it is a really great step forward.

And, as I wanted, it is short, simple, elegant, works perfectly and -specially- shows the power of elisp and how literate programming can be useful and powerful for reproducible research (this is part of my thesis).

I may continue with some questions, but it helps me a lot to learn.

Thank you so much! :D

[-] sachac@lemmy.ml 1 points 4 months ago

Sorry for the late reply here too, and thanks for your e-mail! You've probably already figured out that you can change the :var in the second babel block to point to a different table (ex: :var source=another_table) named with #+NAME: . The tags you've defined with #+TAGS: are file-level, but it's possible to change the function so that it can take an optional argument with a tag hierarchy, so you can make your own structure.

this post was submitted on 15 Sep 2025

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