Output file

[Hermes Sampedro]

Hello, 

I am working with step-29 and I was wondering what is the best way to import the solution vectors (real, imaginary and intensity solutions) into Matlab. Is it possible to export one point of the solution into a txt file? Or what would be the easiest way using Dealii for that?

Thank you

Regards, 

H

[Wolfgang Bangerth]

It depends on what you actually want to do with it. I believe that Matlab can
read VTK or VTU files, but these are tailored towards visualization. If you
want the solution at a small number of individual points, you can evaluate it
with VectorTools::point_value() and then output these values by hand.

Best
W.

--
------------------------------------------------------------------------
Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

[Hermes Sampedro]

Thank you very much for your answer. Is it then not possible to use somehow the DataOut approach presented in step-29 and use a 'txt' parameter in the .prm file?

In case of doing that manually as you suggested, how could I access the real and imaginary parts in the solution vector (step-29)?

Doing something like:

   ofstream myfile;

        myfile.open ("solution.txt");

        myfile << "Point:\t" << VectorTools::point_value(dof_handler,solution,Point<2>(1./3, 1./3));

        myfile.close();

I get an error when running:

dof.get_fe(0).n_components() == 1

Thank you again for the help.

Regards, 

H

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[Wolfgang Bangerth]

On 8/5/21 6:18 AM, Hermes Sampedro wrote:
> Thank you very much for your answer. Is it then not possible to use somehow
> the DataOut approach presented in step-29 and use a 'txt' parameter in the
> .prm file?

That's the wrong question. VTK and VTU files are text files, you can open them
with an editor. The question is not whether it's a text file or a binary file,
but what's in it. As I mentioned, the right question is what you want to do
with the information in the file, and depending on that, you choose a file format.

> In case of doing that manually as you suggested, how could I access the real
> and imaginary parts in the solution vector (step-29)?
>
> Doing something like:
>
> ofstream myfile;
>
> myfile.open ("solution.txt");
>
> myfile << "Point:\t" <<
> VectorTools::point_value(dof_handler,solution,Point<2>(1./3, 1./3));
>
> myfile.close();
>
>
> I get an error when running:
>
>
> dof.get_fe(0).n_components() == 1
>
>
> Thank you again for the help.

You are solving a problem that has more than one component -- the real and
imaginary parts are separate components. You need to call that variation of
the VectorTools::point_value() function that returns its information in the
form of a Vector<double> object.