# MATLAB: How to use fsolve with a system of 2 nonlinear equations in a for that changes a parameter at each iteration

fsolvefsolve loopMATLABnonlinear

Hi everyone, thanks in advance for any help or tip you will give me.
I have a problem about solving a system of 2 nonlinear equation of 2 variables and 1 parameters, the one which would change during every iteraction (I tried to search in other questions opened before mine but it seems i couldn't find anything relatable or solvable for my case).
The problem at the beginning of my matlab code is to find self-consistent solutions of a a system of 2 nonlin. equation in 2 variables, but one of these equations with a parameter that is the components of a given vector V. The result i need is a matrix with the 2 solutions in the rows, and column based on V dimension.
My thought was to use this kind of code, but i dont understand the source of the error "Unable to perform assignment because dot indexing is not supported for variables of this type.".
Am i just using a bad code, or what i need is not solvable by fsolve, and i need another approach?
(Sorry for any mistake, english in not my mother tongue)
Code:
``function F(Cq,Vch,V)        %%variables are Cq and Vch, V should be the parameter    %%...    %%constants definitions    %%..    F(1)= Cq-(K*kB*T)*log(2*(1+cosh((q*Vch))/(kB*T))));    F(2)= Vch -(Vgstop-V)*(Cox/(Cox+0.5*Cq));end%%different file%...% constant definitions%...V=-1:0.01:1;            %%vector of parametersCq0=0;                    %initial guessVch0=0;                    %initial guessfor i=1:length(V)    iterfun=@(Cq,Vch) F(Cq,Vch,V(i)});    ans(i,:)=fsolve(iterfun,Cq0,Vch0);end``

``%%different file%...% constant definitions%...V=-1:0.01:1;            %%vector of parametersCq0=0;                    %initial guessVch0=0;                    %initial guessRoots=cell(1,numel(V));   % preallocate!for i=1:length(V)    iterfun=@(x)Fdd(x,V(i));  Roots{i}=fsolve(iterfun,[Cq0;Vch0]);  % don't name variable as ansendcelldisp(Roots)Roots= [Roots{:}] % double arrayfunction F=Fdd(x,V)        %%variables are Cq and Vch, V should be the parameter    %%...    %%constants definitions    %%..    Cq=x(1);    Vch=x(2);    K=6; % your value    kB=8; % your value    q=10; % your value    T=2; % your value     Vgstop=3; % your value    Cox=4; % your value    F(1)= Cq-(K.*kB.*T).*log(2.*(1+cosh((q.*Vch))./(kB.*T)));    F(2)= Vch -(Vgstop-V).*(Cox./(Cox+0.5.*Cq));end``