Error in sym / privsubsasgn and sym / subsasgn

Hi.

My code is as follows:

t=850
R=10000
xA=0:.01:.99;
xB=1-xA
gIdeal=8.314*t*(xA.*log(xA)+xB.*log(xB));
gA=(-11276.24+(253.048446*t)-38.5844296*t*log(t)+0.018531982*t^(2)-5.764227*10.^(-6)*t^(3)+74092*t^(-1))
gB=(-8162.609+(137.236859*t)-22.8317533*t*log(t)-0.001912904*t^(2)-3.552*10.^(-9)*t^(3)+176667*t^(-1))
gStndrd=xA.*gA+xB.*gB;
gExcess=xA.*xB.*(113246.16-58.0001*t);
gBulk=gIdeal+gStndrd+gExcess
va=(9.78122*10^(-6)+6.745*10^(-10)*t+1.91*10^(-16)*t^(3)+3.76*10^(-6)/t)
vb=(11.99189*10^(-6)+1.485*10^(-10)*t+7.0*10^(-15)*t^(2)+7.84*10^(-6)/t-380*10^(-6)/t^(2))
VAb=va*xA+vb*xB
HAL=0.286;
HSI=0.2;
sigmaAL=0.914*(1-0.725*0.286/R);
AReaAl=1.091*(6.022*10^(23))^(1/3)*va^(2/3);
SIgmaSi=0.773*(1-0.725*0.2/R);
AReaSi=1.091*(6.022*10^(23))^(1/3)*vb^(2/3);
pal=xB.^(2).*(-3143.78+0.39297.*t)+8.314.*t.*log(xA);
psi=xA.^(2).*(113246.16-58.0001.*t)+8.314.*t.*log(xB);
psurfal=0.84*pal;
psurfsi=0.84*psi;
Pspl=psurfal-pal;
Pspi=psurfsi-psi;
syms x
a1=sigmaAL;
a2=SIgmaSi;
a3=8.314;
a4=t;
a5=0:.01:.99
a6=Pspl
a7=Pspi
a8=AReaAl
a9=AReaSi
for i=2:100
    pp=a1+(1/a8)*(a6(i))+((a3*a4)/(a8))*log(x/a5(i))
    qq=a2+(1/a9)*(a7(i))+((a3*a4)/(a9))*log((1-x)/(1-a5(i)))
    rr=qq-pp
    hh(i)=solve(rr,x)
end
a1=sigmaAL;
a2=8.314;
a3=t;
a4=AReaAl;
a5=0:.01:.99
doublea6=double(hh(i));
a6=doublea6;
a7=Pspl;
for i=2:100
    ss(i)=a1+((a2*a3)/a4)*log(a6(i)/a5(i))+(1/a4)*a7(i)
end
ss=real(ss(i))
doublea1=double(VAb);
a1=doublea1;
doublea2=double(ss);
a2=doublea2;
a3=R*10^(-9);
for i=2:100
    tt(i)=(a1(i)*a2(i))/a3;
end
tt=real(tt(i))
doublea1=double(gBulk);
a1=doublea1;
doublea2=double(tt(i));
a2=doublea2;
for i=2:100
    L(i)=a1(i)+a2(i);
end
L=real(L(i))
plot(L(i),xB)

My code has the following error:

In an assignment A(:) = B, the number of elements in A and B must be the same.

Error in sym/privsubsasgn (line 1031)

L_tilde2 = builtin('subsasgn',L_tilde,struct('type','()','subs',{varargin}),R_tilde);

Error in sym/subsasgn (line 868)

C = privsubsasgn(L,R,inds{:});

Error in dimntotal10nm (line 40)

hh(i)=solve(rr,x)

[sterling lin]

Have you solved this problem? I meet the same issue. Could you teach me how to solve that?

Answer 1

[Harshavardhan]

Hi @seema redhu

The error you're encountering is due to trying to assign a value to an array element when the right-hand side of the assignment has a different number of elements than expected. This happens in the line:

hh(i) = solve(rr, x)

The “solve” function can return multiple solutions, which means “hh(i)” might be trying to store multiple values (or none) in a single array element.

If you expect only one solution, ensure that the equation “rr” is structured to have a unique solution. You might need to check the logic of your equations.

If multiple solutions are possible and you want to store them, use a cell array.

hh = cell(1, 100); % Initialise the cell array
for i=2:100
    pp=a1+(1/a8)*(a6(i))+((a3*a4)/(a8))*log(x/a5(i));
    qq=a2+(1/a9)*(a7(i))+((a3*a4)/(a9))*log((1-x)/(1-a5(i)));
    rr=qq-pp;
 hh{i}=solve(rr,x);
end

If you are interested in a specific solution, select it explicitly:

hh= zeros(1,100); %Initializing hh with zeros
for i=2:100
    pp=a1+(1/a8)*(a6(i))+((a3*a4)/(a8))*log(x/a5(i));
    qq=a2+(1/a9)*(a7(i))+((a3*a4)/(a9))*log((1-x)/(1-a5(i)));
    rr=qq-pp;
    solutions=solve(rr,x);
    if(size(solutions,1)>0)%Ensure Solutions has atleast one element
        hh(i)=solutions(1); % Select the first solution, for example
    else
      hh(i)=-1;% Handle no solution, for example
    end
end

For more information on “solve” type the following command in a MATLAB command window:

doc solve

Hope this helps.