--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/python/indep.py Fri May 27 14:24:59 2011 +0530
@@ -0,0 +1,43 @@
+#!/usr/bin/python
+# Determines the first row that is dependent on the previous rows of S.
+# Returns the coefficients of dependence
+
+import pylab as pl
+from makezero import makezero
+
+def indep(S, gap=1e8):
+ S = pl.atleast_2d(S)
+ E = pl.finfo(float).eps
+ r, c = S.shape
+ ind = 1
+ i = 2
+ while ind and i<=r:
+ shortS = S[:i,:]
+ sigma = pl.svd(pl.dot(shortS,shortS.T))[1]
+ if(sigma[-1]/sigma[0] < (E*max(i, c))):
+ ind = 0
+ else:
+ shsig = sigma.copy()
+ shsig[:-1] = sigma[1:]
+ if pl.any(sigma/shsig > gap):
+ ind = 0
+ else:
+ ind = 1
+ i += 1
+ if ind:
+ b = pl.atleast_2d([])
+
+ else:
+ A, B = S[i-1,:], S[:i-1,:]
+ # c = A/B,
+ # c = (B.T\A.T).T
+ c = pl.lstsq(B.T, A.T)[0].T
+# c = pl.solve(B.T, A.T).T
+ c = makezero(c, gap)
+ c = c.squeeze()
+ b = pl.hstack((-c, 1))
+ b = pl.atleast_2d(b)
+ return b
+
+if __name__== "__main__":
+ pass