Solve not returning values after first iteration?

Omega=zeros(181,2)clear

Omega = 181×2

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

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Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

Unrecognized function or variable 'Angle'.

clc
%Lengths of links
r1 = 7.5; r2 = 2.9; r3 = 10.85; r4 = 6.2;
%Angle between two grounds
theta1 = deg2rad(27);
%Starting angle of link 2
theta2deg=-68;
%Reference angles for links 3 and 4
theta3g=12;
theta4g=-37;
a=0
Angle=zeros(181,3);
theta2temp=theta2deg
%Counting loops until colinear
while true
    a=a+1
    theta2temp=theta2temp+2
    if theta2temp>rad2deg(theta1)
        break
    end
end
%Loop for angles of all links until colinear
for i=1:a
    theta2new=theta2deg+2*(i-1)
theta2=deg2rad(theta2new);

f = @(x) [ ...
    r2*cos(theta2) + r3*cos(x(1)) - r4*cos(x(2)) - r1*cos(theta1);
    r2*sin(theta2) + r3*sin(x(1)) - r4*sin(x(2)) - r1*sin(theta1)
];

initial_guess = [deg2rad(theta3g), deg2rad(theta4g)];

options = optimoptions('fsolve','Display','iter');
solution = fsolve(f, initial_guess, options);

theta3 = rad2deg(solution(1));
theta4 = rad2deg(solution(2));

fprintf('Theta3 = %.2f degrees\n', theta3);
fprintf('Theta4 = %.2f degrees\n', theta4);
theta3g=theta3;
theta4g=theta4;
Angle(i,:)=[theta2new,theta3,theta4];
end
%Angles of all links after colinear (angles should be shrinking)
for i=a:181
    theta2new=theta2deg+2*(i-1);
theta2=deg2rad(theta2new);

f = @(x) [ ...
    r2*cos(theta2) + r3*cos(x(1)) - r4*cos(x(2)) - r1*cos(theta1);
    r2*sin(theta2) + r3*sin(x(1)) - r4*sin(x(2)) - r1*sin(theta1)
];
%Angular velocity is greatest here, therefore the guesses must be adjusted
%closer to the desired value to reach it
initial_guess = [(deg2rad(theta3g-5)), (deg2rad(theta4g-5))];
options = optimoptions('fsolve','Display','iter');
solution = fsolve(f, initial_guess, options);
theta3 = rad2deg(solution(1));
theta4 = rad2deg(solution(2));

fprintf('Theta3 = %.2f degrees\n', theta3);
fprintf('Theta4 = %.2f degrees\n', theta4);
theta3g=theta3;
theta4g=theta4;
Angle(i,:)=[theta2new,theta3,theta4];
end
Angle
for a=1:181
    hold on
    Bx=r4*cos(deg2rad(Angle(a,3)));
    By=r4*sin(deg2rad(Angle(a,3)));
    plot(Bx,By,'ro')
    Ax=r2*cos(deg2rad(Angle(a,1)));
    Ay=r2*sin(deg2rad(Angle(a,1)));
    plot(Ax,Ay,'bo')
end
Omega=zeros(181,2);
syms omega3 omega4
for j=1:181
a=r3*cos(deg2rad(Angle(j,2)+90));
b=r4*cos(deg2rad(Angle(j,3)+90));
c=r2*cos(deg2rad(Angle(j,1)+90));
d=r3*sin(deg2rad(Angle(j,2)+90));
e=r4*sin(deg2rad(Angle(j,3)+90));
f=r2*sin(deg2rad(Angle(j,1)+90));
eq1 = omega3*a == omega4*b - 100*c;
eq2 = omega3*d == omega4*e - 100*f ;

% Solve the system
sol = solve([eq1, eq2], [omega3, omega4]);
omega3=double(sol.omega3);
omega4=double(sol.omega4);
Omega(j,1)=omega3
Omega(j,2)=omega4
end
% Store solution in a temporary matrix
%
%
%
%
% My only issue is with the final for loop, I created it in a seperate
% window and got the correct values and now I put it in a loop and the
% inputs are from values I derived earlier (which are correct) yet the loop
% is only returning zeroes and isn't working properly. How can I make a
% loop that solves for the same two equations and two unknowns at different
% inputs and puts all the outputs in a matrix? Thanks!

Answer 1

[Torsten]

You overwrite omega3 and omega4 as symbolic variables with numerical values.

Replace

% Solve the system
sol = solve([eq1, eq2], [omega3, omega4]);
omega3=double(sol.omega3);
omega4=double(sol.omega4);
Omega(j,1)=omega3
Omega(j,2)=omega4

by

% Solve the system
sol = solve([eq1, eq2], [omega3, omega4]);
Omega(j,1)=double(sol.omega3);
Omega(j,2)=double(sol.omega4);