Re: Computations on properties

[Thorsten Jolitz <tjolitz@gmail.com>]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> Thierry Pellé <thierry.pelle@soliavos.fr> writes:
>
>> Hi,
>>   I'm seeking how to do something like that
>>
>> Let the following text inserted in an org-mode file
>>
>> * Mean Calculation
>>  :PROPERTIES:
>>  :VAL1: 5
>>  :VAL2: 10
>>  :COEF: 10
>>  :END:
>>
>> I would like to append the result of a computation 
>> like RES=(VAL1*COEF+VAL2)/(COEF+1) 
>>
>> Something like 
>> * Mean Calculation
>> ...
>>   :END:
>>
>> Mean Calculation=RES (where RES is the value of the result)
>>
>> I think to do this with a python script but is there a more org-mode/emacs
>> method to do it?
>
> Sometimes I think it would be nice to have a way to draw property values
> directly into a babel block, the way you can with table data. Sort of
> like:
>
> * Heading
>   :PROPERTIES:
>   :ID:       3f78f08a-ccca-4fc0-aba9-2a192f7a0e5a
>   :foo:  5
>   :bar:  puppy
>   :END:
>
> #+BEGIN_SRC emacs-lisp :var alist=3f78f08a-ccca-4fc0-aba9-2a192f7a0e5a
>
> And in the block, the "alist" variable would look like '(:foo 5 :bar
> "puppy").
>
> What would be even better would be to run a tags search on matching
> headlines and feed all property drawers into a single block, as a list
> of alists. Just thinking out loud...

This is probably not really what you want, but at least somehow related. I
would not know how to do this via source-block arguments, but maybe you can
use the results of one source-block (that produces the data) as input for
another source-block that does the real work. 

* Heading 1 :match:
  :PROPERTIES:
  :ID:       3f78f08a-ccca-4fc0-aba9-2a192f7a0e5a
  :foo:  5
  :bar:  puppy
  :END:

* Heading 2
  :PROPERTIES:
  :ID:       3f78f08a-ccca-4fc0-aba9-2a192f7a0e5b
  :foo:  6
  :bar: yuppy
  :END:


* Heading 3 :match:
  :PROPERTIES:
  :ID:       3f78f08a-ccca-4fc0-aba9-2a192f7a0e5c
  :foo:  7
  :bar:  hippie
  :END:


#+begin_src emacs-lisp :results raw
   (let ((lst))
      (org-map-entries
       (lambda () (cons (org-entry-properties) lst))
       "match" 'file))
#+end_src

#+results:
((((FILE . /home/tj/News/drafts/drafts/419) (TAGS . :match:) (ALLTAGS
. :match:) (BLOCKED . ) (ID . 3f78f08a-ccca-4fc0-aba9-2a192f7a0e5a) (foo . 5)
(bar . puppy) (CATEGORY . 419))) (((FILE . /home/tj/News/drafts/drafts/419)
(TAGS . :match:) (ALLTAGS . :match:) (BLOCKED . ) (ID .
3f78f08a-ccca-4fc0-aba9-2a192f7a0e5c) (foo . 7) (bar . hippie) (CATEGORY .
419))))

-- 
cheers,
Thorsten