PDE toolbox, specifying coefficients, error telling me "Function specifying a coefficient must accept two input arguments and return one output argument."

Hi every body

In my code the c coefficient in each point of the mesh is the components of the matrix B_HMM, but I don't know how I assign those.

It would be very much appreciated if somebody kindly pointed me into the right direction.

My code is:

model=createpde()
geometryFromEdges(model,g);
applyBoundaryCondition(model,'Edge',1:4,'u',@boundfun);
setInitialConditions(model,0);
generateMesh(model,'Geometricorder','linear');
generateMesh(model,'Hmax',H);
[p,e,t] = meshToPet(model.Mesh);
x = (p(1,t(1,:))+p(1, t(2,:))+p(1,t(3,:)) )/3;
y = (p(2,t(1,:))+p(2, t(2,:))+p(2,t(3,:)) )/3;
mp = [x;y];
macro_mesh.p=p; macro_mesh.e=e; macro_mesh.t=t; macro_mesh.mp=mp;
A_HMM = myHMM(macro_mesh,mp,cellSize,epsilon,aeps);
B_HMM=A_HMM';
specifyCoefficients(model,'m',0,'d',1,'c',@ccoeffunction,'a',0,'f',0);
T=1; dt=.1; N=T/dt;
tlist = 0:dt:T;
results = solvepde(model,tlist);
U_HMM = results.NodalSolution;

function cmatrix = ccoeffunction(location, B_HMM)
n1 = 4;
nr = numel(location.x);
cmatrix = zeros(n1,nr);
cmatrix(1,:) = B_HMM(1,:);
cmatrix(2,:) = B_HMM(2,:);
cmatrix(3,:) = B_HMM(3,:);
cmatrix(4,:) = B_HMM(4,:);
end

What is the problem of introducing of ccoeffunction function?

Of course, I didn't put here the long funcion A_HMM, because it works correctly.