questions about the 'pdeeig'

I'm using the syntax [?,?]=??????(?,?,?,?.1.0,?,1.0,[−1,1]); to solve a PDE on a given domain with a given ? ,

I have two questions about this syntax

How can I extract the matrices of the finite elements system for the PDE i.e ?

and

how I can assure that the computed eigenvalue say ?(2) corresponds to the correct eigenfunction ?(:,2)? I mean are they eigenpairs? is there any way to check that?

Thanks

Answer 1

[Ravi Kumar]

Please use one the newer workflow like general equation based one, Structural or Thermal one. Once you setup your model in one of the newwer workflow you can get matrices using assembleFEMatrices function.

For your second question you can back substitute eigenpair into the equation and make sure the residual is near zero.

Regards,

Ravi

[Haya M]

Thank you Ravi for your answer, would you clarify to me what do you mean by resudue?

[Ravi Kumar]

Knowing v1 and l1, you can compute the residual as:

res = norm(K*v1-l1*v1), this would be close to zero only if l1 and v1 are the right pair.

PS: I fixed typo in my previous comment.

Regards,

Ravi

[Haya M]

Thank you Ravi for the answer,

Do you mean that res = norm((K-l1)*v) ?

best regards,

Haya

[Ravi Kumar]

Yep, that's right. Fixed my comment again.

Ragards,

Ravi