From: Carsten Dominik <dominik@uva.nl>
To: Nicolas Goaziou <n.goaziou@neuf.fr>
Cc: emacs-orgmode@gnu.org
Subject: Re: Spreadsheet and weighted means
Date: Mon, 29 Sep 2008 10:43:14 +0200 [thread overview]
Message-ID: <9136F031-BBCD-4A80-A117-6047C5D3F777@uva.nl> (raw)
In-Reply-To: <87wsh7w589.fsf@selenimh.orion.org>
On Sep 20, 2008, at 9:00 AM, Nicolas Goaziou wrote:
> Hello,
>
> I stumbled upon this problem : I'd like to compute the weighted mean
> of
> some values, even though cells might be empty. In fact, I'm aiming at
> something like this :
>
> | | Coeff. | 0.2 | 0.5 | 1 |
> |-----------+--------+--------+--------+--------|
> | Name | Mean | Test 1 | Test 2 | Test 3 |
> |-----------+--------+--------+--------+--------|
> | Student A | 10 | 15 | 12 | 8 |
> | Student B | 12 | | 16 | 10 |
>
> where 10=(15*0.2+12*0.5+8*1)/(0.2+0.5+1) and 12=(16*0.5+10*1)/(0.5+1)
>
> I just can't guess what has to be put in @3$2 as a column formula to
> calculate those mean means… I perhaps have overlooked something
> simple.
> Anyway, if anyone has a clue here, I will be pleased to hear it.
Hi Nicolas, there s no builtin way to deal with this, in particular
with the fact that you want to treat empty fields as non-existing, and
therefore also to ignore the corresponding weight.
You cou write a Lisp function to do this, though:
(defun my-wmean (values weights)
(let ((vsum 0) (wsum 0))
(while (and values weights)
(setq v (pop values) w (pop weights))
(unless (equal "" v)
(setq vsum (+ vsum (* (string-to-number w) (string-to-number v)))
wsum (+ wsum (string-to-number w)))))
(/ vsum wsum)))
The you could use this as your equation:
| | Coeff. | 0.2 | 0.5 | 1 |
|-----------+--------+--------+--------+--------|
| Name | 0 | Test 1 | Test 2 | Test 3 |
|-----------+--------+--------+--------+--------|
| Student A | 10 | 15 | 12 | 8 |
| Student B | 12 | | 16 | 10 |
#+TBLFM: $2='(wmean '($3..$5) '(@1$3..@1$5));E%d
Note the use of the E flag, to make sure empty fields are not skipped,
but passed through as empty strings.......
Hope this helps.
- Carsten
>
>
> --
> Nicolas Goaziou
>
>
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next prev parent reply other threads:[~2008-09-29 8:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-20 7:00 Spreadsheet and weighted means Nicolas Goaziou
2008-09-29 8:43 ` Carsten Dominik [this message]
2008-09-29 8:44 ` Carsten Dominik
2008-10-01 16:46 ` Nicolas Goaziou
2008-10-01 19:26 ` Carsten Dominik
2008-10-01 19:45 ` Embedded elisp formulas, was: " Eric Schulte
2008-10-01 20:29 ` Paul R
2008-10-02 0:03 ` Eric Schulte
2008-10-02 11:44 ` Carsten Dominik
2008-10-08 23:12 ` ANN: org-eval-light.el was: " Eric Schulte
2008-11-06 1:19 ` Eric Schulte
2008-11-09 7:02 ` Carsten Dominik
2008-11-10 19:51 ` Daniel Clemente
2008-10-04 8:49 ` Nicolas Goaziou
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