Undefined operator '==' for input arguments of type 'struct'. Error in decic (line 41) free_yp = find(fixed_yp0 == 0); Error in IMWFGD (line 111) [y0, yp0] = decic(f, t0, y0est, yp0est, [], opt) >>

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Dursman Mchabe 2018-5-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/401662-undefined-operator-for-input-arguments-of-type-struct-error-in-decic-line-41-free_yp

评论： Dursman Mchabe 2018-5-22

IMWFGD.m

Hi all, I am trying to run a script to solve 10 DAEs, but I get an error message " Undefined operator '==' for input arguments of type 'struct'.

Error in decic (line 41) free_yp = find(fixed_yp0 == 0);

Error in IMWFGD (line 111) [y0, yp0] = decic(f, t0, y0est, yp0est, [], opt)"

Please see the attachment for the script.

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Dursman Mchabe 2018-5-20

Is it a good idea to change the operator "==" to "isequalto"?

Walter Roberson 2018-5-20

"Is it a good idea to change the operator "==" to "isequalto"?"

No.

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Answer 1

Walter Roberson 2018-5-20

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The sixth input to decic needs to be fixed_yp0 . You have passed opt there, and your opt is a structure.

It looks to me as if you omitted the fixed_y0 argument.

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Dursman Mchabe 2018-5-21

Over the past hours, I have tried different ways to pass both fixed_y0 and fixed_yp0, but I did not succeed. For example,

"[y0, yp0] = decic(f, t0, y0est,[], yp0est, [], opt)"

gives the error message

"Not enough input arguments.

Error in symengine>@(t,in2,in3,param1,param2,param3...]

Error in decic (line 66) res = feval(odefun,t0,y0,yp0,varargin{:});

Error in IMWFGD (line 110) [y0, yp0] = decic(f, t0, y0est,[], yp0est, [], opt)"

I have also tried

"[y0, yp0] = decic(f, t0, y0est,0, yp0est, 0, opt)"

"Error using decic (line 44) Cannot specify more than 10 components of y0 and yp0.

Error in IMWFGD (line 110) [y0, yp0] = decic(f, t0, y0est,0, yp0est, 0, opt)"

I also tried to omit the opt, but I got error message that says

"Not enough input arguments. Error in symengine>@(t,in2,in3,param1,param2,param3... Error in decic (line 66) res = feval(odefun,t0,y0,yp0,varargin{:});

Error in IMWFGD (line 110) [y0, yp0] = decic(f, t0, y0est,[], yp0est, [])

Am I passing fixed_y0 and fixed_yp0 correctly?

Dursman Mchabe 2018-5-21

在 MATLAB Online 中打开

IMWFGD1.m

Thanks a lot for your response Guillaume, I followed steps 1 to 6 below:

    %1. Define symbols
    syms a(t) b(t) c(t) d(t) e(t) f(t) g(t) h(t) i(t) j(t) k(t)...
        HSO2 kga DCa2 DSO2 kLa T KSPCaSO3 BETCaSO3 ktot BETCaCO3 MWCaCO3 Kad...
        kCO2 KCO2 HCO2 KSO2 KHSO3 KHCO3 P
    %2. Define equations
    eqs = [diff(a(t),t) + diff(b(t),t) + diff(c(t),t) == (P-HSO2...
            *a(t))/(1/kga)+(HSO2/(1+(DCa2 *g(t))/(DSO2*(a(t) + b(t) + c(t))))...
            *kLa) - 0.162*exp(-5153/T)*(((g(t)*c(t))/KSPCaSO3) - 1)^3 ...
            * (BETCaSO3/((g(t)*c(t))/KSPCaSO3)),diff(d(t),t) + diff(e(t),t)...
            + diff(f(t),t)+ diff(g(t),t) == 0.162*exp(-5153/T)*(((g(t)*c(t))...
            /KSPCaSO3) - 1)^3 * (BETCaSO3/((g(t)*c(t))/KSPCaSO3)),diff(h(t),t)...
            + 2*diff(g(t),t) - diff(b(t),t)- 2* diff(c(t),t) - diff(e(t),t)...
            - 2* diff(f(t),t) - diff(i(t),t) == 0,diff(d(t),t) + diff(e(t),t)...
            + diff(f(t),t) + diff(a(t),t) + diff(b(t),t) + diff(c(t),t) == ...
            -ktot*BETCaCO3*MWCaCO3*j(t)*h(t) *(1-(Kad*h(t))/(1+Kad*h(t)))-...
            0.162*exp(-5153/T)*(((g(t)*c(t))/KSPCaSO3) - 1)^3 ...
            *(BETCaSO3/((g(t)*c(t))/KSPCaSO3)),diff(d(t),t) == (kCO2/KCO2)...
            *e(t) - kCO2*HCO2,h(t)*diff(b(t),t)...
            + b(t)*diff(h(t),t) - KSO2*diff(a(t),t) == 0,h(t)*diff(c(t),t)...
            + c(t)*diff(h(t),t) - KHSO3*diff(b(t),t) == 0,h(t)*diff(e(t),t)...
            + e(t)*diff(h(t),t) - KCO2*diff(d(t),t) == 0,h(t)*diff(f(t),t)...
            + f(t)*diff(h(t),t) - KHCO3*diff(e(t),t) == 0,h(t)*diff(i(t),t)...
            + i(t)*diff(h(t),t)==0];
     %3. Define variables
     vars = [a(t); b(t); c(t); d(t); e(t); f(t); g(t); h(t); i(t); j(t)];
     %4. Rewrite this DAE system to a system of first-order differential algebraic equations.
     [eqs, vars, newVars] = reduceDifferentialOrder(eqs, vars)
     %5. Convert a DAE system to a MATLAB function handle, using daeFunction
     F = daeFunction(eqs, vars, [HSO2, kga, DCa2, DSO2, kLa, T, KSPCaSO3, BETCaSO3, ktot, BETCaCO3, MWCaCO3, Kad,...
        kCO2, KCO2, HCO2, KSO2, KHSO3, KHCO3, P])
     %6. Assign numerical values to the symbolic parameters: HSO2 = 149;
       %kga = 4.14e-6;
       %DCa2 = 1.39e-9;
       %DSO2 = 2.89e-9;
       %kLa = 8.4e-4;
       %T = 323.15;
       %KSPCaSO3 = 1.07e-7;
       %BETCaSO3 = 10;
       %ktot = 8.825e-3;
       %BETCaCO3 = 12.54;
       %MWCaCO3 = 100.0869;
       %Kad = 0.84;
       %kCO2 = 0.1242;
       %KCO2 = 1.7e-3;
       %HCO2 = 5.15e+3;
       %KSO2 = 6.24;
       %KHSO3 = 5.68e-5;
       %KHCO3 = 6.55e-8;
       %P = 47.28325;
     f = @(t, y, yp)  F(t, y, yp, [149,4.14e-6,1.39e-9,2.89e-9,8.4e-4,323.15,1.07e-7,10,8.825e-3,12.54,100.0869,0.84,0.1242,1.7e-3,5.15e+3,6.24,5.68e-5,6.55e-8,1])

Guillaume 2018-5-21

I don't have the symbolic toolbox so can't do any testing and I don't know how daeFunction works.

Something called by f is not happy about the number of arguments it receives. So first checked, that you've passed the right number of arguments to F. Possibly, use the 'File' option of daeFunction to generate an m file instead. It may aid in debugging as it will error on a particular line of the file rather than in an anonymous function.

Dursman Mchabe 2018-5-22