pdebound function form only Dirichlet boundary conditions

Hello,

I wrote a boundary condidion file but somehow it doesnt work later on in the "assempde" command. Maybe I did a mistake mit the boundary condition matrixes. I only have Dirichlet boundary conditions, so I wrote zeros in the q and g matrixes for the Neumann conditions, but I am not sure if this is the right way. The geometry matrixes gd, sf and ns did I export form the pdetool GUI. I have a elliptic skalar pde. I hope someone can help me, because the description is not so clear at the help sites.

if true
  %     dl = decsg(dl, sf, ns)
  [p,e,t] = inimesh(dl)
  [qmatrix,gmatrix,hmatrix,rmatrix] = pdebound(p,e)
  b = @pdebound
  u = assempde(b,p,e,t,1,0,10)
end

And here my funktion file.

if true
   function [qmatrix,gmatrix,hmatrix,rmatrix] = pdebound(p,e)
   ne = size(e,2) % number of edges
qmatrix = zeros(1,ne);
gmatrix = qmatrix;
hmatrix = zeros(1,2*ne);
rmatrix = hmatrix;
regler = 6;
for k = 1:ne
  x1 = p(1,e(1,k)); % x at first point in segment
  x2 = p(1,e(2,k)); % x at second point in segment
  xm = (x1 + x2)/2; % x at segment midpoint
  y1 = p(2,e(1,k)); % y at first point in segment
  y2 = p(2,e(2,k)); % y at second point in segment
  ym = (y1 + y2)/2; % y at segment midpoint
  switch e(5,k)
      case {1,2,3,4} % rectangle boundaries
          hmatrix(k) = 1;
          hmatrix(k+ne) = 1;
          rmatrix(k) = regler*(x1-y1);
          rmatrix(k+ne) = regler*(x2-y2);
      otherwise % same as case {5,6,7,8}, circle boundaries
          qmatrix(k) = 0;
          gmatrix(k) = 0;
  end
end
end

I get always this erros. So I thought it is maybe the fault of my function file like I suggested above?

if true
  Error using pdebound
Too many input arguments.
Error in pdeefxpd (line 10)
[q,g,h,r]=feval(bl,p,e,u,time);
Error in pdeexpd (line 40)
[q,g,h,r]=pdeefxpd(p,e,u,time,bl);
Error in assemb (line 95)
[q,g,h,r]=pdeexpd(p,e,bl);
Error in assempde (line 185)
[Q,G,H,R]=assemb(b,p,e);
end

Answer 1

[Alan Weiss]

I wonder if you simply need to change the signature of your function to

 function [qmatrix,gmatrix,hmatrix,rmatrix] = pdebound(p,e,u,time)

Also, I wonder why you have the pdebound line here:

[p,e,t] = initmesh(dl); % you originally had inimesh, not initmesh
[qmatrix,gmatrix,hmatrix,rmatrix] = pdebound(p,e) % remove this line

Good luck,

Alan Weiss

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