matlab - How do you concatenate the rows of a matrix into a vector?

Question

For an m-by-m (square) array, how do you concatenate all the rows into a column vector with size m^2 ?

Answer 1

There are a couple of different ways you can collapse your matrix into a vector, depending upon how you want the contents of your matrix to fill that vector. Here are two examples, one using the function reshape (after first transposing the matrix) and one using the colon syntax (:):

>> M = [1 2 3; 4 5 6; 7 8 9];    % Sample matrix
>> vector = reshape(M.', [], 1)  % Collect the row contents into a column vector

vector =

     1
     2
     3
     4
     5
     6
     7
     8
     9

>> vector = M(:)  % Collect the column contents into a column vector

vector =

     1
     4
     7
     2
     5
     8
     3
     6
     9