Line 37: Parse error at A: usage might be invalid MATLAB syntax.

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Abul Yasa Hasan 2024-3-16

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https://ww2.mathworks.cn/matlabcentral/answers/2095126-line-37-parse-error-at-a-usage-might-be-invalid-matlab-syntax

评论： Abul Yasa Hasan 2024-3-16

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Ques.) Use Householder's method to place the following matrices in tridiagonal form.

I had a basic code provided by the tutor which I adapted to the problem above. However, when I run the I get the error in Line 37(the second last line) - Parse error at A: usage might be invalid MATLAB syntax.

% Test with the given matrix
A = [4.75 2.25 -0.25; 2.25 4.75 1.25; -0.25 1.25 4.75];
hh_tridiag(A);
alpha = -2.2638, r = 2.2604, w = 0     0.99847     -0.0553
P^(1) =
    1.0000         0         0
         0   -0.9939    0.1104
         0    0.1104    0.9939

A^(2) =
    4.7500   -2.2638   -0.0000
   -2.2638    4.4756   -1.2195
   -0.0000   -1.2195    5.0244
function hh_tridiag(A)
    n = size(A, 1);
    for k = 1:(n-2)
        % Calculate t and alpha
        t = sqrt(sum(A((k+1):end, k).^2));
        if A(k+1, k) ~= 0
            alpha = -sign(A(k+1, k)) * t;
        else
            alpha = -t;
        end
        % Calculate r and w
        r = sqrt((alpha^2 - A(k+1, k) * alpha) / 2);
        w = zeros(n, 1);
        w(k+1) = (A(k+1, k) - alpha) / (2 * r);
        for j = (k+2):n
            w(j) = A(j, k) / (2 * r);
        end
        disp(['alpha = ', num2str(alpha), ', r = ', num2str(r), ', w = ', num2str(w')]);
        % Calculate Householder matrix P
        P = eye(n) - 2 * (w * w');
        disp(['P^(', num2str(k), ') =']);
        disp(P);
        % Update A
        A = P * A * P';
        disp(['A^(', num2str(k+1), ') =']);
        disp(A);
    end
end