--- /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