Why do I receive an error in calling "decic"?

Hey everyone,

I'am trying to solve a DAE-system with the help of ode15s. I already tried ode15i in another code, but had some problems. So I want to check if ode15s performs better.

When computing the consistent initial conditions for ode15i I receive the following error message:

Not enough input arguments.

Error in DGL_Membrane>@(t,y,yp)M(t,y)*yp-F(t,y) (line 101)

implicitDAE = @(t,y,yp) M(t,y)*yp - F(t,y)

Error in decic (line 66)

res = feval(odefun,t0,y0,yp0,varargin{:});

Error in DGL_Membrane (line 102)

[y0,yp0] = decic(implicitDAE,0,y0est,[],yp0est,[],opt);

My code is the following (following the procedure of https://de.mathworks.com/help/symbolic/solve-daes-using-mass-matrix-solvers.html)

function [ySol,tSol] = DGL_Membrane(a,k,L)

syms asym bsym csym dsym fsym hsym isym ksym jsym x(t) y(t) z(t) xx(t) e(t)

Dx = diff(x);

Dy = diff(y);

Dz = diff(z);

Dxx = diff(xx);

Eqn1 = -bsym * diff(x(t),1) - x*bsym*csym*dsym*diff(y(t),1) == asym;

Eqn2 = -fsym*diff(z(t),1) - z * fsym * hsym * dsym * diff(y(t),1) == e;

Eqn3 = -isym*Dxx(t) - xx * isym*jsym * dsym * diff(y(t),1) == ksym;

Eqn4 = csym * x(t) + hsym* z(t) + jsym*xx(t) ==0;

Eqn5 = csym * asym + hsym* e(t) + jsym*ksym == 0;

DAEs=[Eqn1,Eqn2,Eqn3,Eqn4,Eqn5];

DAEvars = [x(t);y(t);z(t);xx(t);e(t)];

[M,f] = massMatrixForm(DAEs,DAEvars);

pDAEs = symvar(DAEs);

pDAEvars = symvar(DAEvars);

extraParams = setdiff(pDAEs, pDAEvars);

M = odeFunction(M, DAEvars,bsym,csym,dsym,fsym,hsym,isym,jsym);

f = odeFunction(f, DAEvars,asym,csym,hsym,jsym,ksym);

% Declare parameters

asym = a;

bsym=1e-6*L; %P1

csym=-1; %Z1

dsym=9.64853321233100184e4/(8.3145*293.15); %F/RT

fsym=0.01e-6*L; %P2

hsym=-2;%Z2

isym=10e-6*L; %P3

jsym=1; %Z3

ksym=k;

c1f=0.2e-3; %feed concentrations mol/m^3

c2f=0.2e-3;

c3f=0.6e-3;

F = @(t,Y) f(t,Y,asym,csym,hsym,jsym,ksym);

y0est = [c1f; 0; c2f;c3f;(-csym * asym - jsym*ksym)/hsym];

yp0est = zeros(5,1);

opt = odeset('Mass', M, 'InitialSlope', yp0est,...

'RelTol', 10.0^(-6), 'AbsTol' , 10.0^(-6));

implicitDAE = @(t,y,yp) M(t,y)*yp - F(t,y)

[y0,yp0] = decic(implicitDAE,0,y0est,[],yp0est,[],opt);

opt = odeset(opt, 'InitialSlope', yp0);

time=linspace(0,L,500);

[tSol,ySol] = ode15s(F,time,y0est,opt);

plot(tSol,ySol(:,[1,3,4,5]),'LineWidth',2)

end

Does anyone have an idea what's wrong with my decic-input?

Thanks for help and best regards !

[Torsten]

decic has 8 inputs, not 7.

[Tobias Hubach]

Hello Torsten,

When I refer to the decic documentation it says 7 inputs (or 6 without options)

https://de.mathworks.com/help/matlab/ref/decic.html

[Torsten]

You are right, it was the symbolic decic function.

I think you will have to define MM the same as F

MM = @(t,y) M(t,y,asym,csym,hsym,jsym,ksym)

and use MM in the definition of implicitDAE.

Answer 1

[Ishu]

Hi Tobias Hubach,

I understand that you are trying to use the "decic" function of MATLAB to solve the differential equations.

I tried to reproduce the error at my end and it also shows me the same error. After that I checked the function handles "M" and "F" and the input arguments required by the handle "M" are a lot not just the "(t,y)". Because of this reason it gives the error of "Not enough input arguments".

Further I looked into the code and found that you are changing the defination of "M" after its initialization. Explained in the given code snippet.

[M,f] = massMatrixForm(DAEs,DAEvars); % you have initialised here
M  

M = 

pDAEs = symvar(DAEs);
pDAEvars = symvar(DAEvars);
extraParams = setdiff(pDAEs, pDAEvars);
M = odeFunction(M, DAEvars,bsym,csym,dsym,fsym,hsym,isym,jsym) % here you have changed "M"

M = function_handle with value:
    @(t,in2,param1,param2,param3,param4,param5,param6,param7)reshape([-param1,0.0,0.0,0.0,0.0,-param1.*param2.*param3.*in2(1,:),-param3.*param4.*param5.*in2(3,:),-param3.*param6.*param7.*in2(4,:),0.0,0.0,0.0,-param4,0.0,0.0,0.0,0.0,0.0,-param6,0.0,0.0,0.0,0.0,0.0,0.0,0.0],[5,5])

Hope it helps.