dolfin team mailing list archive

["Evan Lezar" <evanlezar@xxxxxxxxx>]

On Thu, May 22, 2008 at 12:42 AM, Anders Logg <logg@xxxxxxxxx> wrote:
> On Tue, May 20, 2008 at 09:43:54PM +0200, Evan Lezar wrote:
>> Hi there
>>
>> As an initial attempt, I am trying to use fenics to compute the resonant
>> modes of a rectangular waveguide - and as such I need to solve an
>> eigenvalue problem of the form  [A]x = lambda[B]x where x represents a
>> vector of coefficients of the basis functions used to calculate the
>> entries of the stiffness ([A]) and mass ([B]) matrices.
>>
>> It is easy to assemble the matrices, and I have solved the eigenvalue
>> problem using eigs() ... but now I have the calculated coefficients and
>> I would like to plot the weighted sum of the basis functions (the finite
>> element solution).
>>
>> Any help on the matter would be much appreciated.
>>
>> Thanks
>> Evan
>
> Are you doing this in Python or C++?
>
> If x is the vector, then you can do
>
>  Function u(mesh, x, a);
>
> where a is the form in C++.
>
> In Python, you need to do
>
>  Function u(element, mesh, x);
>
> where element is the FiniteElement you have used for the trial space.
>
> To plot the solution, just do
>
>  plot(u);
>
> --
> Anders
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Thanks for the reply - something is happening now at least :)

Now that I have the function - how do I specify at which coordinates
it should be plotted?  At the moment, there are a couple of vectors
being plotted, but I would like a higher density.

Also, is there a way to plot the mesh as well as the function in viper?

Thanks
Evan



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