Storing values from for-loop into a matrix

Hello, this is my first time using MATLAB. I only have very limited experience using VBA and that has been years since. I have a project for a class, and I can't seem to store my data in a matrix. I am calculating values in a for-loop but cannot increment through the matrix (namely, M_isentropic) since my increment is not an integer. I've found that multivariable for-loops are not an option in MATLAB. Any solution for this? Thanks

p.s. I originally found this code online and have been trying to tweak it to make it work for my incremental situation.

increment = length/0.01;
V = nan(1,increment);
T = nan(1,increment);
ARatio_Inc = nan(1,increment);
M_isentropic = nan(1,increment);
% Set up the solver
for i = 0.00001:0.01:length
    
    length_Inc = 0 + i;
    h_exit_Inc = 2.0*(tan(theta_t) * length_Inc+0.5*h_throat);
    ARatio_Inc = h_exit_Inc / h_throat;
    problem.objective = @(Msup) (1/Msup^2)*(((2+gm1*Msup^2)/gp1)^(gp1/gm1))-ARatio_Inc^2;
    problem.solver    = 'fzero';
    problem.options   = optimset(@fzero);
    % Solve supersonic root
    problem.x0 = [1+1e-6 50];
    M_isentropic(1,i)       = fzero(problem);
    
    % Print solutions to command window
    %  fprintf('==== MATLAB SOLVER ====\n');
    %  fprintf('Msup: %3.4f\n',M_isentropic);
    %  fprintf('=======================\n\n'); 
    % The calculated temperature at each M_isentropic.
    T(1,i) = ((1 + M_isentropic(1,i)^2 * (gamma-1)/2)^-1)*T_stag;
    
    % The calculated velocities at each M_isentropic
    V(1,i) = M_isentropic(1,i)*sqrt(gamma*287.058*T(1,i));
    
end
disp(M_isentropic)

Answer 1

[KSSV]

In MATLAB array indices should be posititve integers, in the given code, i the loop index is used as index in T, V; i is not an integer and it will throw error. So change the code as shown below:

increment = length/0.01;
V = nan(1,increment);
T = nan(1,increment);
ARatio_Inc = nan(1,increment);
M_isentropic = nan(1,increment);
% Set up the solver
count = 0 ; 
for i = 0.00001:0.01:length
    count = count+1 ; 
    length_Inc = 0 + i;
    h_exit_Inc = 2.0*(tan(theta_t) * length_Inc+0.5*h_throat);
    ARatio_Inc = h_exit_Inc / h_throat;
    problem.objective = @(Msup) (1/Msup^2)*(((2+gm1*Msup^2)/gp1)^(gp1/gm1))-ARatio_Inc^2;
    problem.solver    = 'fzero';
    problem.options   = optimset(@fzero);
    % Solve supersonic root
    problem.x0 = [1+1e-6 50];
    M_isentropic(1,i)       = fzero(problem);
    
    % Print solutions to command window
    %  fprintf('==== MATLAB SOLVER ====\n');
    %  fprintf('Msup: %3.4f\n',M_isentropic);
    %  fprintf('=======================\n\n'); 
    % The calculated temperature at each M_isentropic.
    T(1,count) = ((1 + M_isentropic(1,i)^2 * (gamma-1)/2)^-1)*T_stag;
    
    % The calculated velocities at each M_isentropic
    V(1,count) = M_isentropic(1,i)*sqrt(gamma*287.058*T(1,count));
    
end
disp(M_isentropic)

[Rami Abdelhadi]

Thank you so much, this was very helpful

[KSSV]

Thanks is accepting/ voting the answer. :)