1 #!/usr/bin/python

     2 # Determines the first row that is dependent on the previous rows of S. 

     3 # Returns the coefficients of dependence 

     4 

     5 import pylab as pl

     6 from makezero import makezero

     7 

     8 def indep(S, gap=1e8):

     9     S = pl.atleast_2d(S)

    10     E = pl.finfo(float).eps

    11     r, c = S.shape

    12     ind = 1

    13     i = 2

    14     while ind and i<=r:

    15         shortS = S[:i,:]

    16         sigma = pl.svd(pl.dot(shortS,shortS.T))[1]

    17         if(sigma[-1]/sigma[0] < (E*max(i, c))):

    18             ind = 0

    19         else:

    20             shsig = sigma.copy()

    21             shsig[:-1] = sigma[1:]

    22             if pl.any(sigma/shsig > gap):

    23                 ind = 0

    24             else:

    25                 ind = 1

    26                 i += 1

    27     if ind:

    28         b = pl.atleast_2d([])

    29 

    30     else:

    31         A, B = S[i-1,:], S[:i-1,:] 

    32         # c = A/B, 

    33         # c = (B.T\A.T).T

    34         c = pl.lstsq(B.T, A.T)[0].T

    35 #        c = pl.solve(B.T, A.T).T

    36         c = makezero(c, gap)

    37         c = c.squeeze()

    38         b = pl.hstack((-c, 1))

    39         b = pl.atleast_2d(b)

    40     return b

    41 

    42 if __name__== "__main__":

    43     pass