build an array within the loop

i wanna build two arrays within a loop. the first array contain Th2 elements and the second array contain Th3 elements. then i wanna plot them. this my code

for Th2=0:360
d =3.5; a = 1;b = 2; c = 4;

 Th1= 0;
 Z = d*exp(1i*deg2rad(Th1))- a*exp(1i*deg2rad(Th2));
 Zc = conj(Z);
 Ka = c*Zc; Kb = Z*Zc + c^2 -b^2; Kc = c*Z;
 T = roots([ Ka Kb Kc]);
 S = (c*T+Z)/b;
Th3 = rad2deg(angle(S));
Th4 = rad2deg(angle(T));
P= a*exp(1i* deg2rad(Th1))+ 6*exp(1i* deg2rad(Th3+20));

 end 
 plot (Th2,Th3); 

Answer 1

[Charles Rice]

Each time through the loop, Th3 is being overwritten with a new value. You need to assign each new value to the next index in an array.

theta_range = 0:360; % create the range of angles

Th3 = zeros(2, numel(theta_range)); % preallocate array

Th4 = zeros(2, numel(theta_range)); % preallocate array

for theta_index = 1:numel(theta_range)

% step through angles (this helps avoid zero indexing and lets you have a non-integer range)

Th2 = theta_range(theta_index);

d = 3.5;

a = 1;

b = 2;

c = 4;

Th1= 0;

Z = d*exp(1i*deg2rad(Th1)) - a*exp(1i*deg2rad(Th2));

Zc = conj(Z);

Ka = c*Zc;

Kb = Z.*Zc + c^2 - b^2;

Kc = c*Z;

T = roots([ Ka Kb Kc]);

S = (c*T+Z)/b;

Th3(:, theta_index) = rad2deg(angle(S)); % this function gives you a 2x1 result, so put it in both rows

Th4(:, theta_index) = rad2deg(angle(T));

P = a*exp(1i* deg2rad(Th1))+ 6*exp(1i* deg2rad(Th3+20));

end

subplot(2,1,1)

plot(theta_range, Th3(1,:));

xlabel('Theta')

ylabel('Positive Theta 3')

subplot(2,1,2)

plot(theta_range, Th3(2,:));

xlabel('Theta')

ylabel('Negative Theta 3')

[Aamna Alshehhi]

THANKS SO MUCH!!

Answer 2

[Ajay Kumar]

You are not creating Th3 array but overwriting it everytime. Try this

for i=0:360
d =3.5; a = 1;b = 2; c = 4;
 Th1= 0;
 Z = d*exp(1i*deg2rad(Th1))- a*exp(1i*deg2rad(i));
 Zc = conj(Z);
 Ka = c*Zc; Kb = Z*Zc + c^2 -b^2; Kc = c*Z;
 T = roots([ Ka Kb Kc]);
 S = (c*T+Z)/b;
Th3(:,i+1) = rad2deg(angle(S));
Th4 = rad2deg(angle(T));
P= a*exp(1i* deg2rad(Th1))+ 6*exp(1i* deg2rad(Th3+20));
end 
 Th2 = 0:360;
 plot (Th2,Th3(1,:)); 
 hold on;
 plot (Th2,Th3(2,:));

[Aamna Alshehhi]

you guys are AMAZING. THANKS!!!