[SciPy-dev] An addition to basic.py

[Nils Wagner]

Hi all,

it would be nice if the following function could be added to basic.py in
/Lib/linalg

from scipy import *

def vec(a):
    """vec function of the matrix a is the vector formed by stacking
       the columns of a on top of one another
       Reference: Alan J. Laub, Matrix Analysis for Scientists & Engineers
       SIAM 2005
    """
    if not a.iscontiguous():
        a = reshape(a, a.shape)

    return concatenate(transpose(a))
#
# A short test
#
a = rand(3,3)
b = rand(3,3)
c = rand(3,3)
d = dot(a,dot(b,c))
x1 = vec(d)
x2 = dot(linalg.kron(transpose(c),a),vec(b))
print 'x1-x2 should be zero',linalg.norm(x1-x2)

Nils