Re: [O] Unit conversions and symbolic mathematics with Babel

[H. Dieter Wilhelm]

address@hidden (H. Dieter Wilhelm) writes:

> Hello Org,
>
> for some engineering most often I need estimations with unit
> conversions, Emacs Calc is perfect for this.
>
> When it comes to reporting and documentation I'd like to do it with
> org-mode, of course.  For numerical stuff and visualisation purposes I'm
> using already R and TikZ. But for unit conversions and symbolic maths
> I'm in a bind when trying to do this with free programs.
>
> - R :: Do you have experience with a units packages under the R-project?
>   What I've seen so far is not so reassuring...
>
> - Maxima :: I think there is a nice and intuitive units package for
>   maxima.  But this would mean learning an additional tool and mentally
>   switching between both within one document.
>
> - Calc :: I'd prefer to do it with Calc but the Babel interface is
>   (yet?) restricted
>
>   For example, I can define functions and do some unit conversions:
>
>     #+BEGIN_SRC emacs-lisp
>     (defmath cvun(a b)
>         (math-convert-units a b))
>     #+END_SRC
>
>     #+RESULTS:
>     : calcFunc-cvun
>
>     #+BEGIN_SRC calc :var L1 = "5 mm" 
>     cvun( L1, m)
>     #+END_SRC    
>
>     #+RESULTS:
>     : 5e-3 m
>
>   But what is missing is to assign variables within a source block
>   
>     #+BEGIN_SRC calc :var L1 = "5 mm" 
>     L2 := cvun( L1, m)
>     #+END_SRC    
>   
>   Unfortunately this is not working.  Do you have an idea how to
>   implement this?



For your information: Jay Belanger found a workaround

    #+BEGIN_SRC emacs-lisp
    (defmath sett(a b) ; or any other name not identical to the applied lisp 
functions
          (set (nth 2 a) b))
    #+END_SRC

    #+RESULTS:
    : calcFunc-sett

    #+BEGIN_SRC calc :var L1 = 3
    sett( L2, 3.14)
    L2 - L1
    #+END_SRC    

    #+RESULTS:
    : 0.14

-- 
   Dieter   



> - Are you using (better) alternatives?
>
> Thanks for your insights
>
>        Dieter

-- 
Best wishes
H. Dieter Wilhelm
Darmstadt, Germany