can someone explain how i would compute this code

% SO FAR THIS IS THE CODE IVE COMPUTED IM NOT SURE WHERE TO CONTINUE OR IF
% CODE CORRECT SO FAR

u1 = [1; 2; 3];
a1 = 45;
u2 = [0; 1; 0];
a2 = 30;
function qmul(u1, a1, u2, a2)
    % Convert angles from degrees to radians
    a1_rad = deg2rad(a1);
    a2_rad = deg2rad(a2);
    
    % Normalize the Euler axes
    u1 = u1 / norm(u1);
    u2 = u2 / norm(u2);
    
    % Compute quaternions q1 and q2
    epsilon1 = u1 * sin(a1_rad / 2);
    eta1 = cos(a1_rad / 2);
    q1 = [epsilon1; eta1];
    
    epsilon2 = u2 * sin(a2_rad / 2);
    eta2 = cos(a2_rad / 2);
    q2 = [epsilon2; eta2];
    
    % Compute q3 = q1 * q2 using quaternion multiplication
    epsilon3 = cross(epsilon1, epsilon2) + eta1 * epsilon2 + eta2 * epsilon1;
    eta3 = eta1 * eta2 - dot(epsilon1, epsilon2);
    q3 = [epsilon3; eta3];
    
    % Compute Q(q1) matrix
    I = eye(3);
    S_epsilon1 = [0, -epsilon1(3), epsilon1(2);
                  epsilon1(3), 0, -epsilon1(1);
                  -epsilon1(2), epsilon1(1), 0];
    Q_q1 = eta1 * I + S_epsilon1 * epsilon1;
    
    % Compute q3 = Q(q1) * q2 using matrix-vector multiplication
    q3_matrix = Q_q1 * q2;
    
    % Compute the rotation matrix R(q3)
    R_q3 = (eta3 - norm(epsilon3)^2) * I + 2 * epsilon3 * epsilon3' - 2 * eta3 * S(epsilon3);
    
    % Display results
    fprintf('Quaternion q1: [%f, %f, %f, %f]\n', q1);
    fprintf('Quaternion q2: [%f, %f, %f, %f]\n', q2);
    fprintf('Quaternion q3 (quaternion multiplication): [%f, %f, %f, %f]\n', q3);
    fprintf('Quaternion q3 (matrix-vector multiplication): [%f, %f, %f, %f]\n', q3_matrix);
    fprintf('Matrix Q(q1):\n');
    disp(Q_q1);
    fprintf('Rotation matrix R(q3):\n');
    disp(R_q3);
end

[James Tursa]

What exactly are you asking us to help you with? If you want to verify your quaternion multiplication and conversion to rotation matrix code, why not simply compare to results obtained from calling MATLAB functions for this? Keep in mind that MATLAB quaternion functions are in scalar-vector order, whereas your code is in vector-scalar order.

Answer 1

[Image Analyst]

Your function qmul does not compute q1q2, or the rotation matrix Rq3, or print anything out to the command window. Fix those things and then enter in the same sample values they gave you and see if you get the same results as they do.

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[Image Analyst]

By the way, what is the status of our other outstanding question here:

https://www.mathworks.com/matlabcentral/answers/1999088-please-review-matlab-code-and-tell-me-why-i-receive-errors#answer_1276743

You never commented on it or accepted it. We don't like just tossing answers out into a black hole never to hear anything ever again.