MATLAB: Does solve function return an empty value in a for cycle

Question

for i=1:N
    syms Tout
    sol=solve (energy_balance,Tout,'Real',true, 'IgnoreAnalyticConstraints',true);
    T_gp_out(i)=double(sol);
end

Solve function returns an empty value at the second iteration of the for cycle which i am using.

When the solve function is run separately outside the for cycle it returns a real value.

I can't understand what is going wrong when all inputs and syntax are correct.

Should I define a syms vector function outside the for cycle?

Can someone help me?

Thanks in advance.

Giorgio Ceresoli

Answer 1

You have cubic equation

It means that you have 3 roots

try

T_gp_out(i)=double(sol(1));     % choose first root