i want to plot two coordinate positions (complex)

Im working on a project (analysis of four bar linkages) i have two vectors that i would like to plot but dont know how. the vectors i wish to plot are R_A and R_P. shown below my code:

clc, clear
global L1 L2 L3 L4 AP delta 
L1=5;
L2=1;
L3=5;
L4=7;
AP=5;
delta=50;
% Because we want theta2 to range from 0-360 (1rev) and the increment will be 360/200
theta2=0:360/200:360;
theta1=0;
%loop variables
R2=L2*exp(1i*deg2rad(theta2));
%R3=L3*exp(1i*deg2rad(theta3));
%R4=L4*exp(1i*deg2rad(theta4));
R1=L1*exp(1i*deg2rad(theta1));
Z=R1-R2;
Z_con=conj(Z);
%variables of the quadratic equation
a=L4*Z_con;
b=Z.*Z_con+L4^2-L3^2;
c=Z*L4;
%solution of the equation
T=roots([a b c]);
S=(L4*T+Z)/L3;
%angular positions
theta4=rad2deg(angle(T));
theta3=rad2deg(angle(S));
theta_AP=theta3-delta;
%path coordinates of A and P
R3=L3*exp(1i*deg2rad(theta3));
R4=L4*exp(1i*deg2rad(theta4)); %not needed
R_AP=AP*exp(1i*deg2rad(theta_AP));
R_A=R2;
R_P=R2+R_AP;
size(R_A)

ans = 1×2

1 201

size(R_P)

ans = 1×2

602 201

[Dyuman Joshi]

Do you mean like this?

L1=5;
L2=1;
L3=5;
L4=7;
AP=5;
delta=50;

% Because we want theta2 to range from 0-360 (1rev) and the increment will be 360/200
theta2=0:360/200:360;
theta1=0;

%loop variables
R2=L2*exp(1i*deg2rad(theta2));
%R3=L3*exp(1i*deg2rad(theta3));
%R4=L4*exp(1i*deg2rad(theta4));
R1=L1*exp(1i*deg2rad(theta1));
Z=R1-R2;
Z_con=conj(Z);
%variables of the quadratic equation
a=L4*Z_con;
b=Z.*Z_con+L4^2-L3^2;
c=Z*L4;
%solution of the equation
T=roots([a b c]);
S=(L4*T+Z)/L3;
%angular positions
theta4=rad2deg(angle(T));
theta3=rad2deg(angle(S));
theta_AP=theta3-delta;
%path coordinates of A and P
R3=L3*exp(1i*deg2rad(theta3));
R4=L4*exp(1i*deg2rad(theta4)); %not needed
R_AP=AP*exp(1i*deg2rad(theta_AP));
R_A=R2;
R_P=R2+R_AP;
size(R_A)

ans = 1×2

1 201

size(R_P)

ans = 1×2

602 201

plot(R_A,R_P)

Warning: Imaginary parts of complex X and/or Y arguments ignored.

Answer 1

[Vidhi Agarwal]

Hi @shamma aljaberi,

To plot the vectors “R_A” and “R_P” from your four-bar linkage analysis project, you need to ensure that both vectors have compatible dimensions. In provided code snippet there seems a mismatch in the dimensions of “R_A” and “R_P”. ones the dimensions are consistent using “plot” function you can plot the vectors.

Below are the changes in code snippet to resolve the issue of mismatched vector size:

% Initialize T and S
T = zeros(size(theta2));
S = zeros(size(theta2));

% Solve the quadratic equation for each theta2
for k = 1:length(theta2)
    % Coefficients for the quadratic equation
    a = L4 * Z_con(k);
    b = Z(k) * Z_con(k) + L4^2 - L3^2;
    c = Z(k) * L4;
    
    % Solve the quadratic equation
    roots_result = roots([a, b, c]);
    
    % Choose the correct root based on your problem's context
    % Here, we arbitrarily select the first root
    T(k) = roots_result(1);
    S(k) = (L4 * T(k) + Z(k)) / L3;
end

Below is the code snippet to plot the vectors:

% Plotting
figure;
plot(real(R_A), imag(R_A), 'b', 'LineWidth', 2); % Plot R_A
hold on;
plot(real(R_P), imag(R_P), 'r', 'LineWidth', 2); % Plot R_P
title('Path of Points A and P');
xlabel('X Coordinate');
ylabel('Y Coordinate');
legend('Path of A', 'Path of P');
grid on;
axis equal;
hold off;

And output for the same will look like:

For better understanding of “plot” function refer to the following documentation:

• https://www.mathworks.com/help/releases/R2023a/matlab/ref/plot.html

Hope that Helps!