From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Brand <michael.ch.brand@gmail.com>
Subject: Re: Computations on properties
Date: Wed, 9 Oct 2013 21:27:45 +0200
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To: =?ISO-8859-1?Q?Thierry_Pell=E9?= <thierry.pelle@soliavos.fr>
Cc: Org Mode <emacs-orgmode@gnu.org>

Hi Thierry

On Wed, Oct 9, 2013 at 2:19 PM, Thierry Pell=E9 <thierry.pelle@soliavos.fr>=
 wrote:
> Mean Calculation=3DRES (where RES is the value of the result)

One more variant would be to use inline source block calls either
interactively with C-c C-c or during export. An example with shell
(python would be very similar) or the built-in Emacs Lisp is in the
Emacs Regression Test ERT in the top heading "use case of reading
entry properties" here:
http://orgmode.org/w/?p=3Dorg-mode.git;a=3Dblob;f=3Dtesting/examples/babel.=
org

Your use case, here with Emacs Lisp, would be e. g.:

--------------------------------
* Mean Calculation
  :PROPERTIES:
  :VAL1:     5
  :VAL2:     10
  :COEF:     10
  :END:

  Mean Calculation =3D call_mean() =3D5.454545454545454=3D

* code :noexport:
  #+NAME: mean
  #+HEADER: :var val1=3D'nil
  #+HEADER: :var val2=3D'nil
  #+HEADER: :var coef=3D'nil
  #+BEGIN_SRC emacs-lisp :exports none
    (setq
     val1 (string-to-number (org-entry-get
                             org-babel-current-src-block-location "VAL1" t)=
)
     val2 (string-to-number (org-entry-get
                             org-babel-current-src-block-location "VAL2" t)=
)
     coef (string-to-number (org-entry-get
                             org-babel-current-src-block-location "COEF" t)=
))
    (/ (+ (* val1 coef) val2) (+ coef 1.0))
  #+END_SRC
--------------------------------

Michael