Indexing issue- using negative values in for loop calculations.

I would like to store the values Zx and Zy from the code below in Z but not sure how.

clc;
u = 4
Z = zeros(u*u,1);
cx = 1;
cy = 1;
r = 3;

for j = 1:(u*u)
    for x = -u:u
        for y = -u:u
            
            theta = atan2((y-cy) ,(x-cx));
            Zx = cx-r*cos(theta) 
            Zy = cy - r*sin(theta)
            Z(j,1) = (Zx);
            Z(j,2) = (Zy);
            
            
        end
    end 
end

Answer 1

[DGM]

It's not clear why you're overwriting your results and then repeating the process 16 times anyway. If you want Z for all x and all y, then the outer loop doesn't do anything.

u = 4;
Z = zeros(u*u,1);

cx = 1;
cy = 1;
r = 3;

x = -u:u;
y = (-u:u).';

theta = atan2((y-cy) ,(x-cx));
Zx = cx - r*cos(theta)

Zx = 9×9

3.1213 2.8741 2.5435 2.1142 1.5883 1.0000 0.4117 -0.1142 -0.5435 3.3426 3.1213 2.8000 2.3416 1.7276 1.0000 0.2724 -0.3416 -0.8000 3.5725 3.4000 3.1213 2.6641 1.9487 1.0000 0.0513 -0.6641 -1.1213 3.7854 3.6833 3.4962 3.1213 2.3416 1.0000 -0.3416 -1.1213 -1.4962 3.9417 3.9104 3.8460 3.6833 3.1213 1.0000 -1.1213 -1.6833 -1.8460 4.0000 4.0000 4.0000 4.0000 4.0000 -2.0000 -2.0000 -2.0000 -2.0000 3.9417 3.9104 3.8460 3.6833 3.1213 1.0000 -1.1213 -1.6833 -1.8460 3.7854 3.6833 3.4962 3.1213 2.3416 1.0000 -0.3416 -1.1213 -1.4962 3.5725 3.4000 3.1213 2.6641 1.9487 1.0000 0.0513 -0.6641 -1.1213

Zy = cy - r*sin(theta)

Zy = 9×9

3.1213 3.3426 3.5725 3.7854 3.9417 4.0000 3.9417 3.7854 3.5725 2.8741 3.1213 3.4000 3.6833 3.9104 4.0000 3.9104 3.6833 3.4000 2.5435 2.8000 3.1213 3.4962 3.8460 4.0000 3.8460 3.4962 3.1213 2.1142 2.3416 2.6641 3.1213 3.6833 4.0000 3.6833 3.1213 2.6641 1.5883 1.7276 1.9487 2.3416 3.1213 4.0000 3.1213 2.3416 1.9487 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.4117 0.2724 0.0513 -0.3416 -1.1213 -2.0000 -1.1213 -0.3416 0.0513 -0.1142 -0.3416 -0.6641 -1.1213 -1.6833 -2.0000 -1.6833 -1.1213 -0.6641 -0.5435 -0.8000 -1.1213 -1.4962 -1.8460 -2.0000 -1.8460 -1.4962 -1.1213

If you want Zx and Zy to be reshaped as column vectors, figure out how you want them reshaped:

Z = [Zx(:) Zy(:)]

Z = 81×2

3.1213 3.1213 3.3426 2.8741 3.5725 2.5435 3.7854 2.1142 3.9417 1.5883 4.0000 1.0000 3.9417 0.4117 3.7854 -0.1142 3.5725 -0.5435 2.8741 3.3426

[Shrishti Yadav]

Thankyou!!!!!!