Re: [ff3d-users] about derivatives...

[Stephane Del Pino]

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Le lundi 17 Mai 2004 13:46, address@hidden a écrit :
> Hello everybody,
Hello!

> i am trying to write a code in ff3d to solve numerically a model but i have
> a problem :) I have defined a function with the command "function" but if i
> do something like
>
>  d = dx(r);
>
> the compiler says me something like
>
>  cannot compute the derivative of a non FEM function
Yes. Ff3d does not know how to do formal computations... maybe one day...

> So, how can i do this? Is it possible to convert a non FEM function to a
> FEM function? Can somebody help me? Thank a lot to anybody will help me! :)
Yes you can convert explicit functions to FEM functions:

        function u = sin(x)*sin(y)*z;
        femfunction v(M) = u;

Where M is a given mesh.
Then you can use 'dx(v)'.

Best regards,
Stephane.

- -- 
Stéphane Del Pino          Tel: (33)144277170 - Fax: (33)144277200
Laboratoire Jacques-Louis Lions - Université Pierre et Marie Curie
- -+-
http://www.freefem.org
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