Replace specific/diagonal elements in Matrix using editor, scripting

Question

Vincent Hodnett 2020-1-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/499056-replace-specific-diagonal-elements-in-matrix-using-editor-scripting

编辑： Vincent Hodnett 2020-1-6

Hello,

Looking a simple way to replace diagonal values in vector to 0. The matrix is a variance-covariance matrix, however in system will be assuming covariance are

zero, and are independent to each. Have the following matrix:

A = [ 2.5 0.25; 0.25 2.4]
B = flip(A) %Flipped to get in correct orientation to select diagonals 0.25, 0.25
%Not sure if it is possible to select mirrored diagonal in original matrix A

Covariance values are 0.25, which would like to set to zero. However these value could change, therefore if had method to replace these diagonal values with respect to m-row, n-column position, or other method?

If can be selected from original matrix A, would be ideal to avoid flipping.

Thanks in advance

kind rgds

2 个评论
显示无隐藏无

Max Murphy 2020-1-6

Will your system always be a bivariate distribution or will A ever be larger than 2x2?

Vincent Hodnett 2020-1-6

编辑：Vincent Hodnett 2020-1-6

Yes, for this instance. Shall only be 2x2 matrix.Thks

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Max Murphy 2020-1-6

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/499056-replace-specific-diagonal-elements-in-matrix-using-editor-scripting#answer_408826

在 MATLAB Online 中打开

% If this is to be called iteratively
% Example while loop
iteration = 0;
while (iteration < numel(data)) % Some conditional to stay in your loop
    if ~iteration
        % Initially
        % A = [2.5 0; 0 2.4]; % Can you just initialize it with zeros?
        
        % Alternatively, suppose it was imported elsewhere:
        A = [ 2.5 0.25; ... % Top right = A(1,2);
              0.25 2.4];    % Bottom left = A(2,1);
        A = diag(diag(A)); % Keep only diagonal elements
    else
        A(1,2) = cov_ab; % Assume you get this from elsewhere
        A(2,1) = cov_ba;
    end 
    ...
    % Get covariance values 
    doc cov % May be helpful
    ...
    iteration = iteration + 1;
end