how to change the diagonal of a matrix to be the sum of its position on row and column in matlab

You can change the diagonal of a matrix in MATLAB to be the sum of its position on the row and column by using indexing and loops. Here's an example code that takes a square matrix A of size n x n and modifies its diagonal elements:

main.m
n = size(A, 1); % get the size of the matrix, assuming it is square
for i=1:n % loop through the rows of the matrix
    for j=1:n % loop through the columns of the matrix
        if i == j % check if the current element is on the diagonal
            A(i,j) = i + j; % set the element to the sum of its row number and column number
        end
    end
end
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In this code, we first get the size of the matrix using the size function. We then loop through the rows and columns of the matrix using nested for loops. For each element, we check if it is on the diagonal (i.e., if its row index i is equal to its column index j) using an if statement. If it is on the diagonal, we set the element to the sum of its row and column numbers (i+j). Finally, the modified matrix A is returned.