Please help me to plot theta_2 and theta_4 in a graph please. I try this code but the graph shows blank

clear all

% Create constant parameters

a = 400; b = 420; c = 450; d = 650;

% Define constant parameters

K1 = d/a

K2 = d/c

K3 = (((a^2) - (b^2) + (c^2) + (d^2)) / (2*a*c))

figure

hold on

for theta_2 = 55:60

A = cosd(theta_2) - K1 - K2*cosd(theta_2) + K3

B = -2*sind(theta_2)

C = K1 - (K2 + 1)*cosd(theta_2) + K3

theta_4 = 2*atand((-B - sqrt((B^2) - 4*A*C)) / (2*A));

plot(theta_2, theta_4)

end

Answer 1

[Dyuman Joshi]

When plotting a single point at a time, you will have to include a marker, to obtain the points on the figure.

clear all
% Create constant parameters
a = 400; b = 420; c = 450; d = 650;
% Define constant parameters
K1 = d/a;
K2 = d/c;
K3 = (((a^2) - (b^2) + (c^2) + (d^2)) / (2*a*c));
figure
hold on
for theta_2 = 55:60
    A = cosd(theta_2) - K1 - K2*cosd(theta_2) + K3;
    B = -2*sind(theta_2);
    C = K1 - (K2 + 1)*cosd(theta_2) + K3;
    theta_4 = 2*atand((-B - sqrt((B^2) - 4*A*C)) / (2*A));
    %Red hollow circle as a marker
    plot(theta_2, theta_4,'ro')
end

[Dyuman Joshi]

In case you want to plot a line instead of just points, you will need all the points together.

You can vectorize your code to obtain all points together -

clear all
% Create constant parameters
a = 400; b = 420; c = 450; d = 650;
% Define constant parameters
K1 = d/a;
K2 = d/c;
K3 = (((a^2) - (b^2) + (c^2) + (d^2)) / (2*a*c));

figure
%hold on

%theta_2 as a vector
theta_2 = 55:60;

A = cosd(theta_2) - K1 - K2*cosd(theta_2) + K3;
B = -2*sind(theta_2);
C = K1 - (K2 + 1)*cosd(theta_2) + K3;

%Use element-wise operations to obtain theta_4
theta_4 = 2*atand((-B - ((B.^2) - 4.*A.*C).^(1/2))./(2.*A));

%Plot a blue line with asterik markers
plot(theta_2, theta_4,'b-*')

[Bao Long Do]

Thank you very much. It works very well