How to correct the error in specifycoefficient

My function is

function c=ccoef(nodes,elements,~,~,~,~)
N=1;
nr=size(elements,2);
c=zeros(N,nr);
c(1,:)=1/3/(0.02+0.01*20)*ones(1,nr);
a=[];
for i=1:size(nodes,2)    
    if nodes(1,i)>-0.1 && nodes(1,i)<0.1 && nodes(2,i)<=-5 
        a=[a i];
    end
end
[~,col]=find(elements==a(1));
% b=1/3./(0.02+0.01*20);
 
c(:,col(1))=1/3./(0.3+0.01*20);
specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

Error in command window is

Error in pde.PDEModel/specifyCoefficients (line 139)
        coef = pde.CoefficientAssignment(coefcont,argsToPass{:});
Error in fem (line 14)
specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

How to correct this error

kindly help me

[Ravi Kumar]

What is you ccoef2?

Can you simplify the problem and post the complete code that we can run?

[Boni_Pl]

Sir, Can I mail the code to you?

[Boni_Pl]

The equation is

ccoef is the D(r).

model=createpde();

g = @circleg;

geometryFromEdges(model,g);

figure,

pdegplot(model,'EdgeLabels','on')

specifyCoefficients(model,'m',0,'d',0,'c',@ccoef2,'a',@acoef,'f',@fcoef);

generateMesh(model,'Hmax',0.75);

figure,

pdeplot(model);

[Ravi Kumar]

Coefficient functions should use region and state, which contain coordinates and solution values, respectively, to compute the coefficient. You don't need to deal with elements and nodes as you are doing. Refer to simple examples in the documentation page: https://www.mathworks.com/help/pde/ug/pde.pdemodel.specifycoefficients.html

Also, it looks like you are modeling axisymmetric problem, correct? If so, you need to modify the setup a bit as PDE Toolbox uses Cartesian coordinates.