How to solve Index out of bounds because numel(A)=4

Question

U B 2021-2-12

0
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https://ww2.mathworks.cn/matlabcentral/answers/743242-how-to-solve-index-out-of-bounds-because-numel-a-4

评论： KSSV 2021-2-12

My aim is to generate the intensity profile for the output light passing through a polariser and an analyser for different angles of analyser . I am cosidering a gaussian light beam.

gaussian function-

function H = my_gaussian(n, sigma)
two_sigma_sq = 2*sigma*sigma;
H = zeros(n);
for i = 1:n
    for j = 1:n
        x = i - n/2;
        y = j - n/2;
        H(i,j) = exp(-(x*x + y*y)/two_sigma_sq);
    end
end
end

Intensity profile-

H = my_gaussian(256, 50) ;
Ph = 0; E1 = cosd(Ph); E2 = sind(Ph);
E = [E1 ; E2];
Th = [0 30 90];
for i = 1:length(Th)
    A11 = cosd(Th(i))*cosd(Th(i));
    A12 = cosd(Th(i))*sind(Th(i));
    A21 = cosd(Th(i))*sind(Th(i)); 
    A22 = sind(Th(i))*sind(Th(i));
    A = [A11, A12; A21, A22]
    O = A(i)*E
    I = O'*O
    IP = I*H;
figure, imshow(IP);axis image;colorbar;
end

I can put maximum 3 values of Th, it gives me correct answer but as soon as I put 4 values, the 4th value is Incorrect. If I try putting more than 4 values error comes up saying

" Attempted to access A(5); index out of bounds because numel(A)=4.

Error in Untitled2 (line 31)

O = A(i)*E "

What should I change in this program?