form a vector from matrix d even rows with negative valuess in matlab

To form a vector from a matrix d with even rows and negative values in MATLAB, you can use logical indexing along with row and column indexing.

Here is the MATLAB code to achieve this:

main.m
% Example matrix
d = [1, 2, 3;
    -4, 5, -6;
    7, 8, 9;
    -10, -11, 12];

% Logical indexing to select even rows
evenRows = mod(1:size(d, 1), 2) == 0;

% Logical indexing to select negative values
negativeValues = d < 0;

% Combine the conditions to form the vector
resultVector = d(evenRows & negativeValues);

% Display the resulting vector
resultVector
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This code first creates a logical index (evenRows) to select the even rows from the matrix using the mod function. Then, it creates another logical index (negativeValues) to select the negative values from the matrix d. Finally, the two conditions are combined using the & operator to form the vector resultVector containing even rows with negative values.

Output:

main.m
resultVector =

    -4
   -10
   -11
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Note that the values in the resulting vector are the negative values from the even rows of the matrix d.