# solving eigenvalues PDE problem

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Haya M am 20 Mär. 2020
Kommentiert: Ravi Kumar am 23 Mär. 2020
I'm working on solving an eigenvalue problem on a domain . I'm intersted on the eigenvalues on the left hand side of the domain. Hence, I used the pdetool to export the geometry and then generate the mesh (p,e,t) and map it to a certain map. Then I used the syntax 'solvepdeeig' to solve the problem, but Matlab can't accept my input i.e. solvepdeeig(b,e,p,t,1,q,1,r) says there is an erro. I think it only accepts solvepdeeig(model,evr), is there any way to turn this to a model or is there any other syntax to work on with the eigenvalues problems? Especially because I'm looking to extract the finite elements matrices after solving the PDE?
[SL: fixed formatting]
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### Akzeptierte Antwort

Ravi Kumar am 21 Mär. 2020
Hi Haya,
You need to setup the problem using new workflow:
model = createdpde;
Then assign the geometry to the model using decsg and geometryFromEdges functions, first export the geomery using the option in Draw menu of pdetool and then execute the following commands:
g = decsg(gd,sf,ns)
geometryFromEdge(model,g);
The fillin the rest of the details of the model using specifyCoefficient and applyBoundaryConditions function, check for the documentation on the syntax.
Once you are done defining the model, you can generate the mesh and solve for eigenvalue as:
generateMesh(model)
Reign = solvepdeeig(model,[-100, upperFreqLimit])
Regards,
Ravi
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Haya M am 22 Mär. 2020
I got this?
Ravi Kumar am 23 Mär. 2020
Hi Haya,
Were you able to get past this error? I don't think you need to enter anything. Looks like something might have been corrupted in the process. Try saving the setup into a file and reloading in a fresh session of the pdetool. Alternatively, if your geometry is simple, you can create it directly using the decsg() command, check the doc page of decsg().
Regards,
Ravi

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