def cross_product_matrix ( vec ) : return np . array ( [ [ 0 , - vec [ 2 ] , vec [ 1 ] ] , [ vec [ 2 ] , 0 , - vec [ 0 ] ] , [ - vec [ 1 ] , vec [ 0 ] , 0 ] ] )
python 3x3 matrix divided by 1x3
Returns a 3x3 cross - product matrix from a 3 - element vector .
def cross_product_matrix(vec):
    """Returns a 3x3 cross-product matrix from a 3-element vector."""
    return np.array([[0, -vec[2], vec[1]],
                     [vec[2], 0, -vec[0]],
                     [-vec[1], vec[0], 0]])