def a2s ( a ) : s = np . zeros ( ( 6 , ) , 'f' ) # make the a matrix for i in range ( 3 ) : s [ i ] = a [ i ] [ i ] s [ 3 ] = a [ 0 ] [ 1 ] s [ 4 ] = a [ 1 ] [ 2 ] s [ 5 ] = a [ 0 ] [ 2 ] return s
create 5 by 5 matrix in python
convert 3 3 a matrix to 6 element s list ( see Tauxe 1998 )
def a2s(a):
    """
     convert 3,3 a matrix to 6 element "s" list  (see Tauxe 1998)
    """
    s = np.zeros((6,), 'f')  # make the a matrix
    for i in range(3):
        s[i] = a[i][i]
    s[3] = a[0][1]
    s[4] = a[1][2]
    s[5] = a[0][2]
    return s