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

Question

Minjun Bae 2020-1-13

1
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评论： Ravi Kumar 2021-1-19

Hi all,

I keep running into the error while I am specifying coefficients, namely c, a, and f, and the problem is I do not know why.

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

Below is my code:

Mypde = createpde(1);
geometryFromEdges(Mypde, dl);
mesh = generateMesh(Mypde, 'Hmax', 1e-6);

-----------------------

function amatrix = acoeffunction(region,state)
  %Given
gv=-2.7460e-6;
I_tkns=7e-8;
F=9.6485e4;
  %Now define variables
dP = @(state.u) 30*(state.u^4)-60*(state.u)^3+30*(state.u)^2;
E_chem = gv*dP;
E_over = -E_chem/F;
ED_rate = -I_tkns*E_over;
  %Build a matrix for the a coefficient.
n1=2; %length of the vector, representing coefficients 
nr = numel(region.x*region.y) %number of columns, region x and y are multiplied because it is a 2D problem.
amatrix = zeros(n1,nr); %allocate a
amatrix(1,:) = ED_rate*V_li*state.ux/state.u
amatrix(2,:) = ED_rate*V_li*state.uy/state.u

In order for me to test whether the function is correct, I simply put a constant for all other coefficients, and the handle function for a indicated above.

specifyCoefficients(Mypde, 'm', 0, 'd', 1, 'c', 1, 'a', @acoeffunction, 'f', 1)

The error I am getting is shown below:

Error using pde.CoefficientAssignment/checkCoefFcnHdlArgCounts (line
500)
Function specifying a coefficient must accept two
input arguments and return one output argument.
Error in pde.CoefficientAssignment/checkFcnHdlArgCounts (line 273)
            self.checkCoefFcnHdlArgCounts(self.f, systemsize, ndims);
            
Error in pde.CoefficientAssignment (line 105)
      obj.checkFcnHdlArgCounts(systemsize, numdims);
Error in pde.PDEModel/specifyCoefficients (line 139)
        coef =
        pde.CoefficientAssignment(self.EquationCoefficients,argsToPass{:});

Thank you so much in advance.

If you find any other problems in my script, please let me know.

Have a great day.

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mar tav 2021-1-10

Dear MEHDI Heydari

would you please guide me? I have the same problem as you, but my function is

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

I want to assign the B_HMM matrix as the c coefficient.

Ravi Kumar 2021-1-19

The ccoeffunction should take two argument, location, state. You are using second argument to pass additional arguments. You can pass additional argument using a wrapper.

In your main scrtip:

B_HMM = ...

ccoefWrapper = @(location, state) ccoeffunction(location, state, B_HMM)

specifyCoefficients(model,'m',...,'c', ccoefWrapper,'f',...)

Then write the function:

function [cmatrix] = ccoeffunction(location, state,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

You need to fillin appropriately for ... in the example I have shown above.

Regards,

Ravi

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Answer 1

Jothi Saravanan 2020-11-12

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此回答的直接链接

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在 MATLAB Online 中打开

Hi, I am getting the same error. Can someone say what is the mistake I made?

clc; tic;                                              % Clears the screen
clear all;
e=0.5;
mu=0.00689;
V=265.988178;
omega=1047.197;
C=0.0000508;
R=0.508/2;
phi=45;
L=0.127;
%v=12*mu/h^3;
phi=45;
model = createpde();
rect1 = [3, 
    4,
    -1,
    1,
    1,
    -1,
    0.3,
    0.3,
    -0.3,
    -0.3];
r=decsg(rect1);
geometryFromEdges(model,r);
applyBoundaryCondition(model,'dirichlet','Edge',1:4,'u',1*10^5);
specifyCoefficients(model,'m',0,...
                          'd',0,...
                          'c',1,...
                          'a',0,...
                          'f',@fcoeffunction);
generateMesh(model,'Hmax',0.083);
results = solvepde(model);
p= results.NodalSolution;
function f = fcoeffunction(location,state)
N = 1; % Number of equations
nr = length(location.x); % Number of columns
f = zeros(1,nr); % Allocate f
dh=-e*cosd(phi)*sind(location.x+phi)+e*sind(phi)*cosd(location.x+phi);
dt=0.1*omega(e*cosd(phi)*cosd(location.x+phi)+e*sind(phi)*sind(location.x+phi);
o=location.y^2-(L^2/4);
h=C+e*cosd(location.x);
r=(omega*dh+2*dt);
f(1,:)=3*mu*r*o/h^3;
end

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MEHDI Heydari 2020-11-12

在 MATLAB Online 中打开

Hi,

There are some errors in your fcoeffunction. Creat new function save it with the name fcoeffunction and then it will run!

function f = fcoeffunction(location,~)
eA=0.5;
mu=0.00689;
omega=1047.197;
C=0.0000508;
L=0.127;
%v=12*mu/h^3;
phi=45;
nr = length(location.x); % Number of columns
f = zeros(1,nr); % Allocate f
dh=-eA*cosd(phi)*sind(location.x+phi)+eA*sind(phi)*cosd(location.x+phi);
dt=0.1*omega*eA*cosd(phi)*cosd(location.x+phi)+eA*sind(phi)*sind(location.x+phi);
o=location.y.^2-(L^2/4);
h=C+eA*cosd(location.x);
r=(omega*dh+2*dt);
f(1,:)=3*mu*r.*o./(h.^3);
end