Nonconstant coefficients PDE tool: Error telling me that function handle specifying function for coefficient must accept two input argument and return one output argument, yet that is the form that I have

Hello everyone, I'm trying to solve a system of 2PDEs in 1D with nonconstant coefficients (i.e. coefficients dependent on x value and gradient) and I have specified a function for the coefficients and then want to pass it to specifyCoefficients to solve my PDE. I get the following error:

Error using pde.CoefficientAssignment/checkCoefFcnHdlArgCounts (line 531)
Function handle specifying a coefficient must accept two input arguments and return one output argument

What I don't understand is why, since that is the form it is in, i.e. Matrix=function(region, state) so one output, two inputs. Here is the relevant code:

    numberofPDE=2;
model=createpde(numberofPDE);
geometryFromEdges(model,g);
mhandle=@mcoeffunction;
specifyCoefficients(model,'m',mhandle,'c',@ccoeffunction,'d',d,'a',A, 'f', f);
applyBoundaryCondition(model,'Edge',4,'u',@boundary, 'Vectorized','on');
hmax = h/16;
msh = generateMesh(model, 'Hmax', hmax, 'MesherVersion', 'R2013a');
result=solvepde(model);

          where:

function Mmatrix=mcoeffunction(region,~)
  N=4;
  Nr=numel(region.x);
  Mmatrix=zeroes(N,Nr);

I6=width*(2*density2*(y2^5*(- c22^2/5 + (2*c32)/5) - y3^5*(- c22^2/5 + (2*c32)/5) - (c22*y2^4)/2 + (c22*y3^4)/2 - y2^3/3 + y3^3/3 - (c32^2*y2^7)/7 + (c32^2*y3^7)/7 + (c22*c32*y2^6)/3 - (c22*c32*y3^6)/3) - 2*density1*(y1^5*(c21^2/5 + (2*c31)/5) - y2^5*(c21^2/5 + (2*c31)/5) + (c21*y1^4)/2 - (c21*y2^4)/2 + y1^3/3 - y2^3/3 + (c31^2*y1^7)/7 - (c31^2*y2^7)/7 + (c21*c31*y1^6)/3 - (c21*c31*y2^6)/3) - density3*((2*c33^2*y3^7)/7 - (4*c33*y3^5)/5 + (2*y3^3)/3));
I4=width*density3*((2*c33*y3^5)/5 - (2*y3^3)/3) - 2*density1*((c31*y1^5)/5 + (c21*y1^4)/4 + y1^3/3 - (c31*y2^5)/5 - (c21*y2^4)/4 - y2^3/3) - 2*density2*(- (c32*y2^5)/5 + (c22*y2^4)/4 + y2^3/3 + (c32*y3^5)/5 - (c22*y3^4)/4 - y3^3/3);
I2=width*(- 2*density1*(y1^3/3 - y2^3/3) - 2*density2*(y2^3/3 - y3^3/3) - (2*density3*y3^3)/3);

Mmatrix(1,:)=-I2*ones(1,N);
Mmatrix(2,:)=(((pi/(2*L))*sin(pi*region.x./(2*L)))/(1-cos(pi*region.x./(2*L))))*I4;
Mmatrix(4,:)=-I6*ones(1,N);
end

I6, I4, I2 are just numeric values. I have tried with tilde, without tilde, makes no difference. Normally state would be there instead of tilde, but it isn't used here. I get the error from the Mmatrix, since that is the first one it checks.

Anyone have any idea what's going on here? Regards, Leon

Answer 1

[Damian Sheehy]

You may have a syntax error in the body of the mcoeffunction function and the error it is producing may be misdiagnosed. I would suggest testing your function as follows:

% Setup some data to pass to the function
systemsize = 1;
location.x = 0;
location.y = 0;  
location.z = 0;  
location.subdomain=1;  
state.u = zeros(systemsize, 1);  
state.ux = zeros(systemsize, 1);  
state.uy = zeros(systemsize, 1);  
state.uz = zeros(systemsize, 1);  
state.time = 0;

% Now test the function call:  
mhandle=@mcoeffunction;  
result = mhandle(location, state)