From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolas Goaziou <n.goaziou@neuf.fr>
Subject: Re: Spreadsheet and weighted means
Date: Wed, 01 Oct 2008 18:46:02 +0200
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In-Reply-To: <9136F031-BBCD-4A80-A117-6047C5D3F777@uva.nl> (Carsten Dominik's
	message of "Mon, 29 Sep 2008 10:43:14 +0200")
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To: Carsten Dominik <dominik@uva.nl>
Cc: emacs-orgmode@gnu.org

Carsten Dominik <dominik@uva.nl> writes:

Hello,

> 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)))

Well, thank you very much: it does the job.

I don't want to be picky but I'll investigate on a way to have an empty
string instead of a sorry 0 whenever a student hasn't sat for any exam.

Finally, I wondered if it would be useful to make it built-in as
weighted means are somewhat popular in education.

Anyway, thanks again.

-- 
Nicolas Goaziou