find negative elements in matrix and keep their values in matlab

To find negative elements in a matrix and keep their values in MATLAB you can use a combination of loops and conditional statements. One way to do this is by creating a new array, iterating over the original matrix, and checking if each element is negative. If it is, you can add it to the new array. Here's an example code snippet:

main.m
% create a sample matrix
A = [1 -2 3; -4 5 -6; 7 -8 9];

% initialize an empty array to store negative values
negatives = [];

% iterate over the matrix using nested for loops
for i = 1:size(A, 1)
  for j = 1:size(A, 2)
    % check if the element is negative
    if A(i,j) < 0
      % add the negative element to the array
      negatives(end+1) = A(i,j);
    end
  end
end

% display the array of negative values
disp(negatives);
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This will output the following:

main.m
-2 -4 -6 -8
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Note that the end+1 notation is used to add elements to the end of the negatives array. This is because the size of the array is not known beforehand and may change as more negative elements are added.