pdetool identify boundary nodes

After exporting mesh nodes in "p" from pdetool to workspace, I should like to identify those nodes which pdetool assumes are boundary nodes.

Answer 1

[Alan Weiss]

I believe that you can get the [p,e,t] representation of the mesh, and then examine the list of edges e. Look at the indices k where e(6,k) or e(7,k) is 0, meaning an edge of the geometry bordering on the exterior. For details, see the mesh data description. These edges have corresponding points p that are on the boundary of the geometry.

Alan Weiss

MATLAB mathematical toolbox documentation

[Flavio Sartoretto]

Dear Alan, thank you very much for your suggestion. See the attached PDEtool script. I exported "e". I have e(6,:)==1, e(7,:)==0, but there do exist internal nodes!!! Any comment?

[Flavio Sartoretto]

Dear Alan, I analyzed further my "e" matrix. It encloses ONLY boundary edges, no internal ones. Seems strange?!

[Alan Weiss]

PDE Toolbox allows you to set boundary conditions only at edges of the geometry, not internal edges. So perhaps the e matrix consists only of those edges, but I don't know for sure. It might depend on how you created the geometry, whether you removed internal edges or not.

Alan Weiss

MATLAB mathematical toolbox documentation