Hi Nicolas,
On Oct 1, 2008, at 6:46 PM, Nicolas Goaziou wrote:
Carsten Dominik <[EMAIL PROTECTED]> 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.
Well, you can do this by leaving the formatting to the function
instead of the formula under the table:
(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)))))
(if (= vsum 0) "" (format "%.1f" (/ vsum wsum)))))
The you could use this as your equation:
| | Coeff. | 0.2 | 0.5 | 1 |
|-----------+--------+--------+--------+--------|
| Name | | Test 1 | Test 2 | Test 3 |
|-----------+--------+--------+--------+--------|
| Student A | 10.0 | 15 | 12 | 8 |
| Student B | 12.7 | | 16 | 11 |
| Student C | | | | |
#+TBLFM: $2='(my-wmean '($3..$5) '(@[EMAIL PROTECTED]));E
Finally, I wondered if it would be useful to make it built-in as
weighted means are somewhat popular in education.
Well, I could do that, of course. But which version of this
function? What ouput etc?
I guess this would then be the original version, which returns a
number, and which returns 0 if the student has done absolutely
nothing....
- Carsten
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