find elements in row one that are equal to the column number in matlab

One way to find elements in row one that are equal to the column number is to use logical indexing. We can create a logical matrix that is true where the condition is met (i.e., the element in row one is equal to the column number) and false where it is not met. Then, we can use this logical matrix to index into the original matrix to obtain the desired elements.

Here's an example code snippet that demonstrates this approach:

main.m
% Create a sample matrix
A = magic(4);

% Create a logical matrix that is true where row 1 is equal to the column number
[row, col] = size(A);
logical_mat = repmat(1:col, row, 1) == repmat(A(1,:), row, 1);

% Index into the original matrix using the logical matrix to obtain the desired elements
desired_elements = A(logical_mat);
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In this code, magic(4) creates a sample 4x4 matrix, and size(A) is used to obtain the number of rows and columns in the matrix. repmat is used to create two matrices of the same size as A: one with the column numbers repeated for each row, and one with the values in row 1 repeated for each row. These two matrices are then compared element-wise using the == operator to create the logical matrix. Finally, the logical matrix is used to index into A to obtain the desired elements.